What Do You Need To Cite In A Research Paper

You’ll discover that different academic disciplines have different rules and protocols concerning when and how to cite sources, a practice known as “citation.” For example, some disciplines use footnotes, whereas others use parenthetical in-text citations; some require complete bibliographic information on all works consulted, whereas others require only a list of “Works Cited.” As you decide on a concentration and begin advanced work in your department, you’ll need to learn the particular protocols for your discipline. Elsewhere on this website, you’ll find a brief sampling of commonly used citation styles.

The five basic principles described below apply to all disciplines and should guide your own citation practice. Even more fundamental, however, is this general rule: when in doubt, cite. You’ll certainly never find yourself in trouble if you acknowledge a source when it’s not absolutely necessary; it’s always preferable to err on the side of caution and completeness. Better still, if you’re unsure about whether or not to cite a source, ask your professor or preceptor for guidance before submitting the paper or report.

1. Quotation. Any verbatim use of a source, no matter how large or small the quotation, must be placed in quotation marks or, if longer than three lines, clearly indented beyond the regular margin. The quotation must be accompanied, either within the text or in a footnote, by a precise indication of the source, identifying the author, title, place and date of publication (where relevant), and page numbers. Even if you use only a short phrase, or even one key word, you must use quotation marks in order to set off the borrowed language from your own, and you must cite the source.

2. Paraphrase. Paraphrase is a restatement of another person’s thoughts or ideas in your own words, using your own sentence structure. A paraphrase is normally about the same length as the original. Although you don’t need to use quotation marks when you paraphrase, you absolutely do need to cite the source, either in parentheses or in a footnote. If another author’s idea is particularly well put, quote it verbatim and use quotation marks to distinguish that author’s words from your own. Paraphrase your source if you can restate the idea more clearly or simply, or if you want to place the idea in the flow of your own thoughts—though be sure to announce your source in your own text (“Albert Einstein believed that...”) and always include a citation. Paraphrasing does not relieve you of the responsibility to cite your source.

3. Summary. Summary is a concise statement of another person’s thoughts or ideas in your own words. A summary is normally shorter than the original—a distillation of the source’s ideas. When summarizing other people’s ideas, arguments, or conclusions, you must cite your sources—for example, with a footnote at the end of each summary. Taking good notes while doing your research will help you keep straight which ideas belong to which author. Good note-taking habits are especially important when you’re reviewing a series of interpretations or ideas on your subject.

4. Facts, Information, and Data. Often you’ll want to use facts or information to support your own argument. If the information is found exclusively in a particular source, you must clearly acknowledge that source. For example, if you use data from a scientific experiment conducted and reported by a researcher, you must cite your source, probably a scientific journal or a website. Or if you use a piece of information discovered by another scholar in the course of their own research, you must cite your source. But if the fact or information is generally known and accepted—for example, that Woodrow Wilson served as president of both Princeton University and the United States, or that Avogadro’s number is 6.02 x 1023—you do not need to cite a source. Note that facts are different from ideas: facts may not need to be cited, whereas ideas must always be cited. Deciding which facts or pieces of information require citation and which are common knowledge, and thus do not require citation, isn’t always easy. For example, finding the same fact or piece of information in multiple sources doesn’t necessarily mean that it counts as common knowledge. Your best course of action in such a case may be to cite the most credible or authoritative of the multiple sources. Refer to a later section of this website, “Not-So-Common-Knowledge,” for more discussion of how to determine what counts as common knowledge. But remember: when in doubt, cite.

5. Supplementary Information. Occasionally, especially in a longer research paper, you may not be able to include all of the information or ideas from your research in the body of your own paper. In such cases, insert a note offering supplementary information rather than simply providing basic bibliographic information (author, title, place and date of publication, and page numbers). In such footnotes or endnotes, you might provide additional data to bolster your argument, or briefly present an alternative idea that you found in one of your sources, or even list two or three additional articles on some topic that your reader might find of interest. Such notes demonstrate the breadth and depth of your research, and permit you to include germane, but not essential, information or concepts without interrupting the flow of your own paper. Additional claims or analysis of your own that you want to include in your essay without distracting readers from the central line of argument may also appear in footnote form. In these cases, the footnote will not include a citation because the ideas or findings presented belong to you.

In all of the cases above, the standards of academic integrity require both citing the source in the text of your essay and its incorporation into your bibliography. To be clear, it is not enough to simply list a source in your bibliography if it deserves explicit citation in the essay’s body. Failure to provide that citation may result in being charged with plagiarism.

Sometimes, though rarely, a source merits inclusion in your bibliography even when it doesn’t merit a particular citation in your paper’s text. This most often occurs when a source plays a critical role in your understanding of your topic, but never lends a specific idea or piece of evidence to your essay’s argument. For example, imagine you’re writing a paper about totalitarian regimes, and your thinking about such regimes is heavily influenced by your reading of George Orwell’s 1984. Imagine further that nothing from the novel appears explicitly in your essay, and your strongest reference to the book is describing these regimes as “Orwellian” in passing. Here there would be no need to cite 1984 directly, but it would be appropriate to list it in your bibliography. As always, if you’re unsure about a particular case, err on the side of providing a citation and a bibliography entry.

For international students, it’s especially important to review and understand the citation standards and expectations for institutions of higher learning in the United States. Students who have done their college preparation at schools in other countries may have learned research and paper-writing practices different from those at Princeton. For example, students from schools in East Asia may learn that copying directly from sources, without citation, is the proper way to write papers and do research. Students in France, preparing for the Baccalaureate examination, may be encouraged to memorize whole passages from secondary sources and copy them into papers and exam essays. Those cultural differences can sometimes lead to false assumptions about citation practices and expectations at Princeton. Again, you are responsible for reading and understanding the University’s academic regulations as defined and explained in Rights, Rules, Responsibilities. You must ask for assistance from your professors or preceptors if you’re not sure.

The Writing Center, located in Whitman College, is also a key resource for students wanting to learn more about proper note-taking and citation practices. To make an appointment, visit www.princeton.edu/writing/appt or drop in without an appointment Sunday through Thursday evenings.


You will learn about:

  • Plagiarism and how to identify it
  • Paraphrasing a quote or idea

Understand the Consequences

Okay, we are going to get serious here for a minute. Failing to cite your sources equates to plagiarism. Plagiarism is a serious thing that is totally, completely, 100% preventable.  You just need to give credit where credit is due. People do not always give credit for their research, though, and it can get them in a lot of trouble. You can sometimes receive detention or a failing grade.

When Do I Cite?: Direct Quotes

If you choose to use a direct quote, make sure you place quotation marks (these: “”) around it and include a citation.

This shows that you are using someone else’s words to strengthen your paper, which is okay, as long as you properly quote and cite it!

You are using a direct quote in your paper if you are taking someone’s exact words and putting them into your paper. If you have too many direct quotes in your paper, your style may seem a little choppy. Try to paraphrase when possible!

Effective Paraphrasing

When you are writing a research project, most of the ideas you come across during your research, and use to support your research, should be put into your own words. This is also known as paraphrasing.

An effective paraphrase contains the same idea,concept, and tone as the original source, but must be written originally by you.

When you are using other people’s ideas in your research, you must cite them! Even if you put them in your own words.

Example of a Poorly-Worded Paraphrase

Original Quote:

“There is historic justice in trying to rectify a crime committed a half-century ago that galvanized the architectural preservation movement.”

Kimmelman, Michael. “Restore a Gateway to Dignity. A Proposal to Penn Station and Madison Square Garden.” The New York Times, 8 Feb. 2012. http://www.nytimes.com/2012/02/12/arts/design/a-proposal-for-penn-station-and-madison-square-garden.html.

Example of a BAD PARAPHRASE:

History will be made right, but only if an effort is made to remedy the devastation that happened 50 years ago (and sparked the architectural preservation movement).

The sentence structure is essentially the same, and while the words are different and this was not pulled directly out of the article, it is obvious this was copied from the idea of the author and is not cited. This is plagiarism.

Other Examples of Plagiarism

Here are some other ways that people plagiarize:

  • Providing false or incorrect information about the source
  • Using an essay someone else wrote
  • Purchasing a paper and submitting it as your own
  • Not citing sources properly or writing a fake citation

Common Knowledge

When information is considered common knowledge, you do not need to cite it. But how do you know when something is common knowledge?

Common knowledge is information generally known by most people. For example, in a social studies paper you would not need to cite that the White House is located in Washington, D.C. because that is something most people know, especially the audience reading your paper (e.g., your classmates or instructor).

Always cite statistics. Even if you use a statistic that is considered common knowledge (e.g., divorce rates are around 50%, more than half of Americans are overweight or obese), you should find a reputable source to confirm this information.


You have learned:

  • Failing to cite your sources equates to plagiarism
  • You must cite all sources used in writing your research project
  • Most of the ideas used to support your research should be put into your own words; otherwise known as paraphrasing
  • You do not need to cite common knowledge
  • There is more than one way to plagiarize

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