Cite Sources

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You’ve probably heard your teacher or professor talk about the importance of including citations in your research papers. But what exactly are citations? Why are they so important, and what are the different types? Read on for citation basics.

Here’s a table of contents for this guide:  

What is a Citation?

Citation examples, why do we have citations.

Common Mistakes

5 tips for making the perfect citation, troubleshooting.

To begin, let’s examine what a citation actually is. A citation is how you let your readers know that you used information from outside sources in your work. It also describes those sources, and provides information that allows the reader to track them down. This information could be the author’s name, the publication date, or page numbers. The exact information included in the citation depends on the citation style you are using. Please see the citation manual for your chosen style for more specifics on how to make your citations in that style. Popular styles include MLA formatting , Chicago style, and APA style.

Having to write citations may seem like another boring step in the paper writing process. However, correctly citing sources in your research projects will ensure that you receive a better grade and create something that uniquely contributes to the subject area you are studying.

It doesn’t matter if you use MLA formatting , APA formatting, or any other citation style. Citing sources is something you should always do.

Here are just a few reasons why it is important for you to cite sources in your work:

Citations Provide Hard Evidence of Your Thesis/Ideas

Citing sources that back up your claim, otherwise known as your thesis statement, creates credibility for you as a researcher. It also opens up room for fact-checking and further research.

Citations Give Credit to the Right People

Citing sources ensures that your reader or teacher can differentiate your original thoughts from the ideas in your sources and of other researchers in your subject area. This ensures that the sources you use receive proper credit for the author’s work, and that as the student, you receive deserved recognition for your unique contributions to the topic. Citations serve as a natural way to place your work within in the broader context of a subject area, and are an easy way for your teacher or professor to gauge your commitment to the project at hand. Going above and beyond in your work is always a good idea!

Citations Promote Originality and Prevent Plagiarism

The point of research projects is not to regurgitate information that can already be found elsewhere. We have Google for that! What your project should aim to do is promote an original idea or put a spin on an existing idea, and use credible sources to promote that idea. Copying or directly referencing a source without proper citations can lead to not only a poor grade, but accusations of academic dishonesty. By backing up your ideas with credible sources, you can easily avoid the trap of plagiarism, and promote further research on their topic. To help people find your unique perspective on your topic and create consistency throughout your work, it is always a good idea to use a specific, standardized citation style, such as APA format or MLA format.

Where Do We Have Citations, and What are the Types of Citations?

Citations typically can be found in two places: at the end of a paper in a bibliography or reference list, and within the text. The latter, sometimes called “in-text” citations, usually consist of a few details about the source, and are generally written in parenthesis at the end of the sentence where you referenced the source.

When Scout meets Boo Radley in To Kill a Mockingbird, she realizes that his reputation does not match his true character (Lee 85).

The citation in the reference list or bibliography corresponds with the in-text citation, and provides more holistic information about the source that you are citing. Publication information is included, as well as a list of all contributors to the source.

Lee, Harper. To Kill a Mockingbird. Perennial Modern Classics, 2006.

Note that each citation style has its own formatting rules regarding in-text and bibliographic citations. An APA citation will have similar information but look different from an MLA citation . Consult the style manual of your chosen citation style for more information.

When Should I Make Citations?

You should make a citation for a source whenever you:

● Directly quote a source ● Paraphrase information from a source ● Use an idea that is expressed in another source ● Make a specific reference to the work of another person

Let’s have a moment of silence for anyone out there who just received a graded paper filled with those dreaded red marks. Ugh. Nothing is worse than spending hours and hours pouring your heart and soul into a research paper, only to receive a failing grade or an accusation of plagiarism (gasp!) due to incorrect citations. It’s tough enough finding quality resources, analyzing them, and writing a high quality paper, but to receive marks off for incorrect citing totally crushes the soul.

We know there are so many rules to follow when it comes to citing sources. We’re here to highlight some of the most common citation mistakes students and scholars make when developing their research projects. Check out our top 5 below. Perhaps you’ll recognize a mistake or two you’ve been making in your own work.

If you’re looking for some extra help or guidance, check out the Citation Machine plagiarism and grammar checker. Write your paper, pop it into our “smart proofreader” and watch the magic happen. We’ll provide suggestions for citations and grammar edits so you can worry less about those dreaded red marks and more on your learning. Try it out now!

1. Forgetting to include in-text and parenthetical citations

You’ve found the perfect piece of information to include in your paper. Cool! As you’ve learned throughout school, you need to include a citation for that source in your bibliography or works cited list. Don’t forget to also include an in-text or parenthetical citation in the body of your project.

>Remember, every time outside information is added into a paper, you need to provide the reader with a glimpse as to where that information came from. You can do this with an in-text or parenthetical citation, which includes the author’s name in the sentence or directly after it, in parentheses. Depending on the citation style, you may also need to include the page number or year the source was published.

Here’s an example of how an MLA in-text citation could look in an assignment:

Stockett describes Celia as, “probably ten or fifteen years younger than me, twenty-two, twenty-three, and she’s real pretty” (37).

This excerpt is taken from page 37 in Kathryn Stockett’s book, The Help . In the works cited page at the end of the paper, the reader is provided with a full citation that shares the title of the book, the publisher, the year it was published, and possibly some other key pieces of information, depending on the citation style.

Every piece of information added into a paper needs two citations: a brief one in the body of the project and the full citation on the final page. Bam!

2. Period placement gone wrong

Inside? Outside? Outside and inside? It can be tricky to determine where to place those pesky little periods when including parenthetical citations.

For the majority of citation styles, the period is placed on the outside of the parentheses. Here’s a visual to help you out:

“It’s just that sometimes, our future is dictated by what we are, as opposed to what we want” (Sparks 59).

3. In-text and parenthetical citation overload

If you’re using the same reference over and over in one paragraph, it isn’t necessary to include an in-text or parenthetical citation after each sentence. Instead, save it for the end. The reader will be able to ascertain that all of the information from that single paragraph pertains to the individual in-text or parenthetical citation you’ve included.

4. Using the incorrect citation style or switching between two

Even though there are thousands (yes, thousands!) of citation styles available on Citation Machine, make sure to choose just one style for your project. Not sure whether to choose MLA formatting , APA , Chicago style format or another? Check to see if it’s included in the the assignment’s guidelines. Still not sure? Ask your teacher or school librarian. Whichever style you choose to roll with, make sure it’s consistent throughout the entire project. Remember, citations are included to help readers understand where information originated. If you choose to use various citation styles, it could cause some major confusion.

5. Problems with paraphrasing

A proper paraphrase involves taking someone else’s idea and rewriting it using your own words, in your own writing style. What it’s not is taking someone else’s idea and replacing the words with synonyms. Don’t be a synonym swapper. That’s plagiarism!

If you’re having a tough time trying to paraphrase another author’s words, try this out: Carefully read the text again. When you’re through, put it to the side, and think about what you just read. What was the author’s message? Now, rewrite it, using your own words and writing style. Remember to add an in-text or parenthetical citation at the end of the paraphrase and include the full citation in the works cited or reference page.

When you’re in a rush to meet a deadline and hand in your paper ASAP, it can be all too easy to make a mistake that can cost you big time. Citations are an often-overlooked component of a research paper that, when done correctly, can help you get your best grade yet. So how can you be sure that your citations are helping you achieve success? Here are some tips to take your research paper to the next level.

1. Include In-text or Parenthetical Citations When Paraphrasing

It can be tempting to just re-write a sentence from a source to include in your paper. But neglecting inclusion of a parenthetical, or in-text citation can lead to accusations of plagiarism. Being accused of committing plagiarism can not only impact your grade, but can put your enrollment in jeopardy as well. To avoid making this error, be sure to paraphrase carefully, and include a parenthetical or in-text citation in your paper each time you reference an outside source.

2. Periods (Almost) Always Go After the Parenthesis

Something as minor as an incorrectly placed period after a reference can lead to losing major points on your paper. In nearly every citation style with parenthetical citations, the period comes after the parenthesis, not before. Here is an example of a correctly placed period after a reference in APA format :

(Smith, 2005).

3. Be Consistent with Your Citation Style

Some classes require you use MLA format , while others require APA, while still others require Chicago Manual of Style . These specifications can be difficult to keep track of, but being consistent with your style is perhaps the easiest thing you can do to make sure you have well written citations. Double-checking your citations at the end of your paper before handing it in can lead to good last minute improvements.

4. All In-text and Parenthetical Citations Should Correspond with a Reference List Entry

In-text and parenthetical citations can be done while you are writing your paper, and are included each time you include information from an outside source. It is important to remember, however, that each time you do this, you should bear in mind that at the end of your paper in the works cited, bibliography, reference list, etc., there should be a corresponding longer reference to that same source that matches the in-text or parenthetical reference. When you are finished making your in-text and parenthetical references, use them to make a list of full citations you will need to include at the end of your paper.

5. Cite Properly, Not in Excess

While it is important to include citations in your paper, you shouldn’t be including them after each and every sentence you write. The important thing to remember is to cite only if you are including information from an outside source. This information should only be included if you feel that it backs up your claim effectively enough to the point where another researcher could potentially find that source and identify it as being related to your argument. If all the information in one paragraph you write refers to the same source, you only need to include one in-text or parenthetical citation in that paragraph, not after each individual sentence.

Solution #1: Identifying where to place a period in an in-text citation

1. If the in-text citation is at the end of the sentence or quotation, place a period after the citation (outside the parenthesis).

APA examples:

The results of Singh’s (2021) experiment were inconclusive (p. 42).

“The origin of the two variables could not be determined” (Singh, 2021, p. 42).

MLA examples:

The results of Singh’s experiment were inconclusive (42).

“The origin of the two variables could not be determined” (Singh 42).

2. Always use periods after the phrase “et al.”.

As Gregory Cheffsworth, et al. (2021) suggest, “sour cream can be used as a milk substitute whenever one is low on ingredients and willingness to go to the store” (p. 12).

“Sour cream can be used as a milk substitute whenever one is low on ingredients and willingness to go to the store” (Cheffsworth et al., 2021, p. 12).

As Gregory Cheffsworth, et al. suggest, “sour cream can be used as a milk substitute whenever one is low on ingredients and willingness to go to the store” (p. 12).

“Sour cream can be used as a milk substitute whenever one is low on ingredients and willingness to go to the store” (Cheffsworth et al. 12).

3. Block quotations in APA and MLA place the citation after the period.

A block quotation in APA is a quotation that is longer than forty words. The entire block quotations are indented by 0.5-inches.

            I wanted to make a casserole, but I soon realized that I did not have milk. However, as Gregory Cheffsworth, et al. (2021) suggest,

“Sour cream can be used as a milk substitute whenever one is low on ingredients and willingness to go to the store but, when one encounters this situation, they must be prepared to adapt to the differences in flavor profiles by incorporating new spices.” (p. 12)

In MLA, if the quotation is longer than four lines, use a block quotation by indenting the entire paragraph 0.5-inches.

MLA example:

            I wanted to make a casserole, but I soon realized that I did not have milk. However, as Gregory Cheffsworth, et al. suggest,

Sour cream can be used as a milk substitute whenever one is low on ingredients and willingness to go to the store but, when one encounters this situation, they must be prepared to adapt to the differences in flavor profiles by incorporating new spices. Depending on the selections, the sour cream’s natural taste can be emphasized or completely neutralized. As a result, one should not be afraid of the “sour” in sour cream. (12)

Solution #2: How to choose which citation style to use

Solution #3 When and how to create a direct quote versus a paraphrased citation

Example of a direct quote:

            I wanted to make a casserole, but I soon realized that I did not have milk. However, as Gregory Cheffsworth (2021) suggests, “sour cream can be used as a milk substitute whenever one is low on ingredients and willingness to go to the store” (p. 47).

Example of a paraphrased citation:

            I wanted to make a casserole, but I soon realized that I did not have milk. However, I may be able to use sour cream instead of milk (Cheffsworth, 2021).

Finished with your citations and paper? Check out Citation Machine’s handy paper checker ! It can help you spot errors and polish your paper. There’s also a free  grammar guides library where you can learn what is a verb , an adjective definition , relative pronoun examples , and other grammar-related topics.

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Using Evidence: Citing Sources Properly

What to Consider

Plagiarism detection & revising skills video playlist, citing sources video playlist, related resources.

Citing sources properly is essential to avoiding plagiarism in your writing. Not citing sources properly could imply that the ideas, information, and phrasing you are using are your own, when they actually originated with another author. Plagiarism doesn't just mean copy and pasting another author's words. Review Amber's blog post, "Avoiding Unintentional Plagiarism," for more information! Plagiarism can occur when authors:

Read more about how to avoid these types of plagiarism on the following subpages and review the Plagiarism Detection & Revision Skills video playlist on this page. For more information on avoiding plagiarism, see our Plagiarism Prevention Resource Kit .

Also make sure to consult our resources on citations to learn about the correct formatting for citations.

Citation issues can appear when writers use too much information from a source, rather than including their own ideas and commentary on sources' information. Here are some factors to consider when citing sources:

Remember that the cited material should illustrate rather than substitute for your point. Make sure your paper is more than a collection of ideas from your sources; it should provide an original interpretation of that material. For help with creating this commentary while also avoiding personal opinion, see our Commentary vs. Opinion resource.
The opening sentence of each paragraph should be your topic sentence , and the final sentence in the paragraph should conclude your point and lead into the next. Without these aspects, you leave your reader without a sense of the paragraph's main purpose. Additionally, the reader may not understand your reasons for including that material.
All material that you cite should contribute to your main argument (also called a thesis or purpose statement). When reading the literature, keep that argument in mind, noting ideas or research that speaks specifically to the issues in your particular study. See our synthesis demonstration for help learning how to use the literature in this way.
Most research papers should include a variety of sources from the last 3-5 years. You may find one particularly useful study, but try to balance your references to that study with research from other authors. Otherwise, your paper becomes a book report on that one source and lacks richness of theoretical perspective.
Direct quotations are best avoided whenever possible. While direct quotations can be useful for illustrating a rhetorical choice of your author, in most other cases paraphrasing the material is more appropriate. Using your own words by paraphrasing will better demonstrate your understanding and will allow you to emphasize the ways in which the ideas contribute to your paper's main argument.

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How Do I Cite Sources?

This depends on what type of work you are writing, how you are using the borrowed material, and the expectations of your instructor.

First, you have to think about how you want to identify your sources. If your sources are very important to your ideas, you should mention the author and work in a sentence that introduces your citation. If, however, you are only citing the source to make a minor point, you may consider using parenthetical references, footnotes, or endnotes.

There are also different forms of citation for different disciplines. For example, when you cite sources in a psychology paper you would probably use a different form of citation than you might in a paper for an English class.

Finally, you should always consult your instructor to determine the form of citation appropriate for your paper. You can save a lot of time and energy simply by asking "How should I cite my sources," or "What style of citation should I use?" before you begin writing.

In the following sections, we will take you step-by-step through some general guidelines for citing sources.

Identifying Sources in the Body of Your Paper

The first time you cite a source, it is almost always a good idea to mention its author(s), title, and genre (book, article, or web page, etc.). If the source is central to your work, you may want to introduce it in a separate sentence or two, summarizing its importance and main ideas. But often you can just tag this information onto the beginning or end of a sentence. For example, the following sentence puts information about the author and work before the quotation:

Milan Kundera, in his book The Art of the Novel, suggests that “if the novel should really disappear, it will do so not because it has exhausted its powers but because it exists in a world grown alien to it.”

You may also want to describe the author(s) if they are not famous, or if you have reason to believe your reader does not know them. You should say whether they are economic analysts, artists, physicists, etc. If you do not know anything about the author, and cannot find any information, it is best to say where you found the source and why you believe it is credible and worth citing. For example,

In an essay presented at an Asian Studies conference held at Duke University, Sheldon Geron analyzes the relation of state, labor-unions, and small businesses in Japan between 1950s and 1980s.

If you have already introduced the author and work from which you are citing, and you are obviously referring to the same work, you probably don't need to mention them again. However, if you have cited other sources and then go back to one you had cited earlier, it is a good idea to mention at least the author's name again (and the work if you have referred to more than one by this author) to avoid confusion.

Quoting Material

What is quoting.

Taking the exact words from an original source is called quoting. You should quote material when you believe the way the original author expresses an idea is the most effective means of communicating the point you want to make. If you want to borrow an idea from an author, but do not need his or her exact words, you should try paraphrasing instead of quoting.

How Often Should I Quote?

Most of the time, paraphrasing and summarizing your sources is sufficient (but remember that you still have to cite them!). If you think it’s important to quote something, an excellent rule of thumb is that for every line you quote, you should have at least two lines analyzing it.

How Do I Incorporate Quotations in My Paper?

Most of the time, you can just identify a source and quote from it, as in the first example above. Sometimes, however, you will need to modify the words or format of the quotation in order to fit in your paper. Whenever you change the original words of your source, you must indicate that you have done so. Otherwise, you would be claiming the original author used words that he or she did not use. But be careful not to change too many words! You could accidentally change the meaning of the quotation and falsely claim the author said something they did not.

For example, let's say you want to quote from the following passage in an essay called "United Shareholders of America," by Jacob Weisberg:

The citizen-investor serves his fellow citizens badly by his inclination to withdraw from the community. He tends to serve himself badly as well. He does so by focusing his pursuit of happiness on something that very seldom makes people happy in the way they expect it to.

When you quote, you generally want to be as concise as possible. Keep only the material that is strictly relevant to your own ideas. So here you would not want to quote the middle sentence, since it is repeated again in the more informative last sentence. However, just skipping it would not work -- the final sentence would not make sense without it. So, you have to change the wording a little bit. In order to do so, you will need to use some editing symbols. Your quotation might end up looking like this:

In his essay, “United Shareholders of America,” Jacob Weisberg insists that “The citizen-investor serves his fellow citizens badly by his inclination to withdraw from the community. He tends to serve himself badly... by focusing his pursuit of happiness on something that very seldom makes people happy in the way they expect it to.”
“He tends to serve himself focusing his pursuit of happiness on [money].”

The brackets around the word [money] indicate that you have substituted that word for other words the author used. To make a substitution this important, however, you had better be sure that [money] is what the final phrase meant -- if the author intentionally left it ambiguous, you would be significantly altering his meaning. That would make you guilty of fraudulent attribution. In this case, however, the paragraph following the one quoted explains that the author is referring to money, so it is okay.

As a general rule, it is okay to make minor grammatical and stylistic changes to make the quoted material fit in your paper, but it is not okay to significantly alter the structure of the material or its content.

Quoting within Quotes

When you have "embedded quotes," or quotations within quotations, you should switch from the normal quotation marks ("") to single quotation marks ('') to show the difference. For example, if an original passage by John Archer reads:

The Mountain Coyote has been described as a “wily” and “single-minded” predator by zoologist Lma Warner.

your quotation might look like this:

As John Archer explains, “The Mountain Coyote has been described as a 'wily' and 'single-minded' predator by zoologist Lma Warner.”

How Do I Include Long Quotes in My Paper?

The exact formatting requirements for long quotations differ depending on the citation style. In general, however, if you are quoting more than 3 lines of material, you should do the following:

For example, a properly-formatted long quotation in a document might look like this:

Akutagawa complicates the picture of picture of himself as mere “reader on the verge of writing his own text,” by having his narrated persona actually finish authoring the work in wich he appears. In the forty-ninth segment of the text, entitled “A Stuffed Swan,” he writes:Using all of his remaining strength, he tried to write his autobiography. Yet it was not an easy task for him. This was due to his still lingering sense of pride and skepticism... After finishing “A Fool's Life,” he accidentally discovered a suffered swan in a used goods store. Although it stood with its head raised, even its yellowed wings had been eaten by insects. He thought of his entire life and felt tears and cruel laughter welling up inside. All that remained for him was madness or suicide.With this gesture Akutagawa ironizes the impossibility of truly writing the self by emphasizing the inevitable split that must occur between writing and written “self,” the Akutagawa still writing “A Fool's Life” cannot possibly be identical with the narrated persona which has finished the work.

Listing References

What's a bibliography.

A bibliography is a list of all of the sources you have used in the process of researching your work. In general, a bibliography should include:

OK, So What's an Annotated Bibliography?

An annotated bibliography is the same as a bibliography with one important difference: in an annotated bibliography, the bibliographic information is followed by a brief description of the content, quality, and usefulness of the source.

What Are Footnotes?

Footnotes are notes placed at the bottom of a page. They cite references or comment on a designated part of the text above it. For example, say you want to add an interesting comment to a sentence you have written, but the comment is not directly related to the argument of your paragraph. In this case, you could add the symbol for a footnote. Then, at the bottom of the page you could reprint the symbol and insert your comment. Here is an example:

This is an illustration of a footnote.1 The number “1” at the end of the previous sentence corresponds with the note below. See how it fits in the body of the text? 1 At the bottom of the page you can insert your comments about the sentence preceding the footnote.

When your reader comes across the footnote in the main text of your paper, he or she could look down at your comments right away, or else continue reading the paragraph and read your comments at the end. Because this makes it convenient for your reader, most citation styles require that you use either footnotes or endnotes in your paper. Some, however, allow you to make parenthetical references (author, date) in the body of your work. See our section on citation styles for more information.

Footnotes are not just for interesting comments, however. Sometimes they simply refer to relevant sources -- they let your reader know where certain material came from or where they can look for other sources on the subject. To decide whether you should cite your sources in footnotes or in the body of your paper, you should ask your instructor or see our section on citation styles.

Where Does the Little Footnote Mark Go?

Whenever possible, put the footnote at the end of a sentence, immediately following the period or whatever punctuation mark completes that sentence. Skip two spaces after the footnote before you begin the next sentence. If you must include the footnote in the middle of a sentence for the sake of clarity, or because the sentence has more than one footnote (try to avoid this!), try to put it at the end of the most relevant phrase, after a comma or other punctuation mark. Otherwise, put it right at the end of the most relevant word. If the footnote is not at the end of a sentence, skip only one space after it.

What's the Difference between Footnotes and Endnotes?

The only real difference is placement -- footnotes appear at the bottom of the relevant page, while endnotes all appear at the end of your document. If you want your reader to read your notes right away, footnotes are more likely to get your reader's attention. Endnotes, on the other hand, are less intrusive and will not interrupt the flow of your paper.

If I Cite Sources in the Footnotes (or Endnotes), How's that Different from a Bibliography?

Sometimes you may be asked to include these -- especially if you have used a parenthetical style of citation. A "works cited" page is a list of all the works from which you have borrowed material. Your reader may find this more convenient than footnotes or endnotes because he or she will not have to wade through all of the comments and other information in order to see the sources from which you drew your material. A "works consulted" page is a complement to a "works cited" page, listing all of the works you used, whether they were useful or not.

Isn't a "Works Consulted" Page the Same as a "Bibliography," Then?

Well, yes. The title is different because "works consulted" pages are meant to complement "works cited" pages, and bibliographies may list other relevant sources in addition to those mentioned in footnotes or endnotes. Choosing to title your bibliography "Works Consulted" or "Selected Bibliography" may help specify the relevance of the sources listed.

For more information on documenting sources, see Purdue University's Online Writing Lab .

University of Denver

University libraries, research guides, a guide to computer science research.

Why do I need to cite my sources?

When should i cite a source, how do i cite a source, quick tools for auto-formatting your citations:, understand the generic format of a citation:.

Imagine research as a conversation -- scholars are trading ideas back and forth and building on the findings of earlier work. Citing your sources is an important part of contributing to this conversation -- it allows readers to understand how your work fits into the overall conversation.

Citing your sources in a standard style also helps readers tell at a glance what type of source you used (book vs. journal article, etc), and it helps readers find and reference the sources you used.

What is Plagiarism?

The  DU Honor Code  defines plagiarism as "including any representation of another's work or ideas as one's own in academic and educational submissions."

At DU, plagiarism is seen as a form of academic misconduct and can result in severe consequences. These explanations of the most common  types of plagiarism  from Bowdoin College can help you learn to detect plagiarism in your own and other's work.

The text above is a direct quote from the Northern Arizona University e-Learning Center's  Academic Integrity @ NAU tutorial. The e-Learning Center was paraphrasing Princeton University's guidelines.

What is Plagiarism Detection Software?

DU uses a plagiarism detection software called VeriCite . When a student turns in a paper through Canvas, VeriCite checks the internet and many databases to see if anything has been copied from another person’s work.

Common Citation Styles:

DU Main users may access

Online Style Guides:

Want to use a program that not only creates your bibliography automatically, but can also store and organize citations and PDFs?

Just need to format a few citations right now? Try these quick tools:

Whichever program you choose, remember to proofread the citations it generates for you!

If you understand the general anatomy of a citation, it's easier to create your own citations -- plus, you can tell at a glance what kind of source was cited. Here's the anatomy of two sources formatted in the CSE (Council of Science Editors) style:

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How to Cite Sources | Citation Generator & Quick Guide

Citing your sources is essential in  academic writing . Whenever you quote or paraphrase a source (such as a book, article, or webpage), you have to include a  citation crediting the original author.

Failing to properly cite your sources counts as plagiarism , since you’re presenting someone else’s ideas as if they were your own.

The most commonly used citation styles are APA and MLA. The free Scribbr Citation Generator is the quickest way to cite sources in these styles. Simply enter the URL, DOI, or title, and we’ll generate an accurate, correctly formatted citation.

Generate accurate citations with Scribbr

The Scribbr Citation Generator will automatically create a flawless APA citation

The Scribbr Citation Generator will automatically create a flawless MLA citation

Table of contents

When do you need to cite sources, which citation style should you use, in-text citations, reference lists and bibliographies.

Scribbr Citation Generator

Other useful citation tools

Citation examples and full guides, frequently asked questions about citing sources.

Citations are required in all types of academic texts. They are needed for several reasons:

A citation is needed whenever you integrate a source into your writing. This usually means quoting or paraphrasing:

Citations are needed whether you quote or paraphrase, and whatever type of source you use. As well as citing scholarly sources like books and journal articles, don’t forget to include citations for any other sources you use for ideas, examples, or evidence. That includes websites, YouTube videos , and lectures .

Usually, your institution (or the journal you’re submitting to) will require you to follow a specific citation style, so check your guidelines or ask your instructor.

In some cases, you may have to choose a citation style for yourself. Make sure to pick one style and use it consistently:

If in doubt, check with your instructor or read other papers from your field of study to see what style they follow.

In most styles, your citations consist of:

Scribbr Citation Checker New

The AI-powered Citation Checker helps you avoid common mistakes such as:

cite your references appropriately

In-text citations most commonly take the form of parenthetical citations featuring the last name of the source’s author and its year of publication (aka author-date citations).

An alternative to this type of in-text citation is the system used in numerical citation styles , where a number is inserted into the text, corresponding to an entry in a numbered reference list.

There are also note citation styles , where you place your citations in either footnotes or endnotes . Since they’re not embedded in the text itself, these citations can provide more detail and sometimes aren’t accompanied by a full reference list or bibliography.

A reference list (aka “Bibliography” or “Works Cited,” depending on the style) is where you provide full information on each of the sources you’ve cited in the text. It appears at the end of your paper, usually with a hanging indent applied to each entry.

The information included in reference entries is broadly similar, whatever citation style you’re using. For each source, you’ll typically include the:

The exact information included varies depending on the source type and the citation style. The order in which the information appears, and how you format it (e.g., capitalization, use of italics) also varies.

Most commonly, the entries in your reference list are alphabetized by author name. This allows the reader to easily find the relevant entry based on the author name in your in-text citation.


In numerical citation styles, the entries in your reference list are numbered, usually based on the order in which you cite them. The reader finds the right entry based on the number that appears in the text.

Vancouver reference list example

Because each style has many small differences regarding things like italicization, capitalization , and punctuation , it can be difficult to get every detail right. Using a citation generator can save you a lot of time and effort.

Scribbr offers citation generators for both APA and MLA style. Both are quick, easy to use, and 100% free, with no ads and no registration required.

Just input a URL or DOI or add the source details manually, and the generator will automatically produce an in-text citation and reference entry in the correct format. You can save your reference list as you go and download it when you’re done, and even add annotations for an annotated bibliography .

Once you’ve prepared your citations, you might still be unsure if they’re correct and if you’ve used them appropriately in your text. This is where Scribbr’s other citation tools and services may come in handy:

Plagiarism Checker

Citation Checker

Citation Editing

Plagiarism means passing off someone else’s words or ideas as your own. It’s a serious offense in academia. Universities use plagiarism checking software to scan your paper and identify any similarities to other texts.

When you’re dealing with a lot of sources, it’s easy to make mistakes that could constitute accidental plagiarism. For example, you might forget to add a citation after a quote, or paraphrase a source in a way that’s too close to the original text.

Using a plagiarism checker yourself before you submit your work can help you spot these mistakes before they get you in trouble. Based on the results, you can add any missing citations and rephrase your text where necessary.

Try out the Scribbr Plagiarism Checker for free, or check out our detailed comparison of the best plagiarism checkers available online.

Scribbr Plagiarism Checker

Scribbr’s Citation Checker is a unique AI-powered tool that automatically detects stylistic errors and inconsistencies in your in-text citations. It also suggests a correction for every mistake.

Currently available for APA Style, this is the fastest and easiest way to make sure you’ve formatted your citations correctly. You can try out the tool for free below.

If you need extra help with your reference list, we also offer a more in-depth Citation Editing Service.

Our experts cross-check your in-text citations and reference entries, make sure you’ve included the correct information for each source, and improve the formatting of your reference page.

If you want to handle your citations yourself, Scribbr’s free Knowledge Base provides clear, accurate guidance on every aspect of citation. You can see citation examples for a variety of common source types below:

And you can check out our comprehensive guides to the most popular citation styles:

At college level, you must properly cite your sources in all essays , research papers , and other academic texts (except exams and in-class exercises).

Add a citation whenever you quote , paraphrase , or summarize information or ideas from a source. You should also give full source details in a bibliography or reference list at the end of your text.

The exact format of your citations depends on which citation style you are instructed to use. The most common styles are APA , MLA , and Chicago .

The abbreviation “ et al. ” (Latin for “and others”) is used to shorten citations of sources with multiple authors.

“Et al.” is used in APA in-text citations of sources with 3+ authors, e.g. (Smith et al., 2019). It is not used in APA reference entries .

Use “et al.” for 3+ authors in MLA in-text citations and Works Cited entries.

Use “et al.” for 4+ authors in a Chicago in-text citation , and for 10+ authors in a Chicago bibliography entry.

The Scribbr Citation Generator is developed using the open-source Citation Style Language (CSL) project and Frank Bennett’s citeproc-js . It’s the same technology used by dozens of other popular citation tools, including Mendeley and Zotero.

You can find all the citation styles and locales used in the Scribbr Citation Generator in our publicly accessible repository on Github .

APA format is widely used by professionals, researchers, and students in the social and behavioral sciences, including fields like education, psychology, and business.

Be sure to check the guidelines of your university or the journal you want to be published in to double-check which style you should be using.

MLA Style  is the second most used citation style (after APA ). It is mainly used by students and researchers in humanities fields such as literature, languages, and philosophy.

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Cite your sources

What is a Citation?

A citation identifies for the reader the original source for an idea, information, or image that is referred to in a work.

Citation basics

From:  Lemieux  Library,  University  of Seattle 

Why Should You Cite?

Quoting Are you quoting two or more consecutive words from a source? Then the original source should be cited and the words or phrase placed in quotes. 

Paraphrasing If an idea or information comes from another source,  even if you put it in your own words , you still need to credit the source.  General vs. Unfamiliar Knowledge You do not need to cite material which is accepted common knowledge. If in doubt whether your information is common knowledge or not, cite it. Formats We usually think of books and articles. However, if you use material from web sites, films, music, graphs, tables, etc. you'll also need to cite these as well.

Plagiarism is presenting the words or ideas of someone else as your own without proper acknowledgment of the source. When you work on a research paper and use supporting material from works by others, it's okay to quote people and use their ideas, but you do need to correctly credit them. Even when you summarize or paraphrase information found in books, articles, or Web pages, you must acknowledge the original author.

Citation Style Help

Helpful links:

For additional writing resources specific to styles listed here visit the  Purdue OWL Writing Lab

Citation and Bibliography Resources

Writing an annotated bibliography

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Land Acknowledgement

The land on which we gather is the unceded territory of the Awaswas-speaking Uypi Tribe. The Amah Mutsun Tribal Band, comprised of the descendants of indigenous people taken to missions Santa Cruz and San Juan Bautista during Spanish colonization of the Central Coast, is today working hard to restore traditional stewardship practices on these lands and heal from historical trauma.

The land acknowledgement used at UC Santa Cruz was developed in partnership with the Amah Mutsun Tribal Band Chairman and the Amah Mutsun Relearning Program at the UCSC Arboretum .

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Citing sources: overview.

Manage your references

Use these tools to help you organize and cite your references:

If you have questions after consulting this guide about how to cite, please contact your advisor/professor or the writing and communication center .

Why citing is important

It's important to cite sources you used in your research for several reasons:

About citations

Citing a source means that you show, within the body of your text, that you took words, ideas, figures, images, etc. from another place.

Citations are a short way to uniquely identify a published work (e.g. book, article, chapter, web site).  They are found in bibliographies and reference lists and are also collected in article and book databases.

Citations consist of standard elements, and contain all the information necessary to identify and track down publications, including:

Citations may look different, depending on what is being cited and which style was used to create them. Choose an appropriate style guide for your needs.  Here is an example of an article citation using four different citation styles.  Notice the common elements as mentioned above:

Author - R. Langer

Article Title - New Methods of Drug Delivery

Source Title - Science

Volume and issue - Vol 249, issue 4976

Publication Date - 1990

Page numbers - 1527-1533

American Chemical Society (ACS) style:

Langer, R. New Methods of Drug Delivery. Science 1990 , 249 , 1527-1533.

IEEE Style:

R. Langer, " New Methods of Drug Delivery," Science , vol. 249 , pp. 1527-1533 , SEP 28, 1990 .

American Psychological Association   (APA) style:

Langer, R. (1990) . New methods of drug delivery. Science , 249 (4976), 1527-1533.

Modern Language Association (MLA) style:

Langer, R. " New Methods of Drug Delivery." Science 249.4976 (1990) : 1527-33.

What to cite

You must cite:

Publications that must be cited include:  books, book chapters, articles, web pages, theses, etc.

Another person's exact words should be quoted and cited to show proper credit 

When in doubt, be safe and cite your source!

Avoiding plagiarism

Plagiarism occurs when you borrow another's words (or ideas) and do not acknowledge that you have done so. In this culture, we consider our words and ideas intellectual property; like a car or any other possession, we believe our words belong to us and cannot be used without our permission.

Plagiarism is a very serious offense. If it is found that you have plagiarized -- deliberately or inadvertently -- you may face serious consequences. In some instances, plagiarism has meant that students have had to leave the institutions where they were studying.

The best way to avoid plagiarism is to cite your sources - both within the body of your paper and in a bibliography of sources you used at the end of your paper.

Some useful links about plagiarism:

Academic Integrity at MIT logo

Academic Integrity at MIT

A handbook for students, search form, avoiding plagiarism - cite your source.

Whenever you take information from a source, whether that source is published on paper, presented in a lecture or broadcast, or made available online, you must tell your reader where the information came from:  that is, you must cite your source .

What does it mean to “cite” a source?

In writing a paper or report, it means:

You show, in the body of your paper, where the words or information came from, using an appropriate formatting style.

You provide complete information about the source (author, title, name of publication, date, etc.) at the end of your paper, in the bibliography (also called the works cited or references page, depending on the style you use).

Note: Different disciplines use different citation styles , as do various journals within a single discipline. If you are unsure which to use, check with your instructor.

In giving formal presentations, it means:

You acknowledge, on your slide, where the graph, chart or other information came from.

In writing a computer program, it means:

You use comments to credit the source of any code you adapted from an open source site or other external sources. Generally, providing a URL is sufficient. You also need to follow the terms of any open source license that applies to the code you are using.

Why should I cite my sources?

To show your readers that you have done your research.

To give credit to others for work they have done.

To point your readers to sources that may be useful to them.

To allow your readers to check your sources, if there are questions.

Citing sources points the way for other scholars. Future generations of engineers, scientists and leaders will look to work done at MIT to solve some of the world’s greatest problems. Citation helps that process continue.

What should I cite?

Print sources:   books, journal articles, newspaper – any material published on paper.

Electronic sources:

In short, any material published or made available on the Internet.

Data: geospatial (GIS) data, Census, economic and other types of data published by governments, data from surveys, economic indicators, bioinformatics data.

Images: charts, graphs, tables, illustrations, architectural plans, photographs.

Recorded material: television broadcasts, podcasts or public speeches.

Spoken material:   personal conversations, interviews, information obtained in lectures, poster sessions, or scholarly presentations of any kind.

Get Help With Citations


Citing Sources

Why Do We Cite Our Research?

Sources of information are cited in order to give the original authors/creators proper credit for their work and to document where an author heard or read the fact or idea that has been incorporated into a new work. The purpose of citations is to let the reader know where you obtained information so sources can easily be located and consulted.

Because knowledge is a cumulative process built on the research and writing of other researchers, your instructor needs to see the quality of the sources you used and how you developed your ideas.

 To get started and to see examples, select the citation style from the dropdown menu on the left.

What Information Should Be Cited and Why?

In general, you must document sources when you provide information that you ordinarily would not have known before conducting your research, and when you provide information that it cannot be assumed the reader knows. You must cite a reference when you:

While you are doing research and locating sources, be sure to document materials thoroughly, noting the author, title, publisher, place of publication, date, and page numbers of all sources used. For electronic materials, you should also note the DOI number (Digital Object Identifier) if available. Note the URL of any website you consult; depending on the source, you may need it for the reference.

APA style no longer requires a database name for most references; MLA style still requires it as part of your citation. In either case, make a note of it in case you need to retrieve it at a later date.

Common Knowledge

Things that are common knowledge do not require citation. For example:

However, if someone draws an original conclusion from a common fact, then you must cite the source:

Also, common sayings or proverbs need not be cited:

Below is a famous saying you might recognize, but it's actually from a poem by Sir Walter Scott. If you read this in a book, of course, you would cite the book. If you already knew this expression, you should still give Sir Walter Scott credit for it because it has a distinct and identifiable origin.

Getting started

We understand that citing your sources can be a little confusing, but it doesn't have to be overwhelming. Before you start, ask yourself these questions:

1. What type of source am I trying to cite?

2. Where did I retrieve that source?

3. What citation style am I supposed to use for my assignment?

Once you've answered these questions, select the most appropriate option from either the  APA  or  MLA  dropdown menu on the left to see examples.

Remember, individual help is always available through the  Center for Academic Enhancement  or email a Holy Family librarian at [email protected]


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  2. Citing a Book in APA

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  3. How to Cite Sources (with Sample Citations)

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  4. Works Cited Alphabetical Order Generator

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  5. References, citations and avoiding plagiarism

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  6. How Do I Cite My Source In Text

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  1. Using Citations

  2. Easiest way to cite References in Research

  3. How to Use Mendeley Part 1

  4. *citation required

  5. What and When to Cite

  6. Evaluating Citations


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  7. Cite Your Sources

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  8. Overview

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  9. Avoiding Plagiarism

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