You will discover that different academic disciplines have different rules and protocols concerning citation -- when and how to cite sources. For example, some disciplines use more traditional footnote form and others use numerical markers in the text; some require complete bibliographic information on all works consulted and others append only a "List of Works Cited." As you decide on a concentration and begin advanced work in your department, you will need to learn the particular protocols for your discipline. At the end of this booklet, you will find a brief sampling of more commonly used bibliographic formats.

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

1. Direct Quotation. Any verbatim use of the text of a source, no matter how large or small the quotation, must be clearly acknowledged. Direct quotations 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, 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 cite the source.

2. Paraphrase. If you restate another person’s thoughts or ideas in your own words, you are paraphrasing. Paraphrasing does not relieve you of the responsibility to cite your source. You should never paraphrase in the effort to disguise someone else’s ideas as your own. If another author’s idea is particularly well put, quote it verbatim and use quotation marks to distinguish his or her 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. If you paraphrase your source, you do not need to use quotation marks. However, you still do need to cite the source, either in your text or a footnote. You may even want to acknowledge your source in your own text ("Albert Einstein believed that…"). In such cases, you still need a footnote.

3. Summary. Summarizing is a looser form of paraphrasing. Typically, you may not follow your source as closely, rephrasing the actual sentences, but instead you may condense and rearrange the ideas in your source. Summarizing the ideas, arguments, or conclusions you find in your sources is perfectly acceptable; in fact, summary is an important tool of the scholar. Once again, however, it is vital to acknowledge your source -- perhaps with a footnote at the end of your paragraph. Taking good notes while doing your research will help you keep straight which ideas belong to which author, which is especially important if you are reviewing a series of interpretations or ideas on your subject.

4. Facts, Information, and Data. Often you will want to use facts or information you have found in your sources to support your own argument. Certainly, if the information can be found exclusively in the source you use, you must clearly acknowledge that source. For example, if you use data from a particular scientific experiment conducted and reported by a researcher, you must cite your source, probably a scientific journal or a Web site. Or if you use a piece of information discovered by another scholar in the course of his or her own research, you must acknowledge your source. Or perhaps you may find two conflicting pieces of information in your reading -- for example, two different estimates of the casualties in a natural catastrophe. Again, in such cases, be sure to cite your sources.

Information, however, is different from an idea. Whereas you must always acknowledge use of other people’s ideas (their conclusions or interpretations based on available information), you may not always have to acknowledge the source of information itself. You do not have to cite a source for a fact or a piece of information that 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. Often, however, deciding which information requires citation and which does not is not so straightforward. Refer to the later section in this booklet, Not-So-Common Knowledge, for more discussion of this question.

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, you may want to insert a note offering supplementary information rather than simply providing basic bibliographic information (author, title, date and place of publication, and page numbers). In such footnotes or endnotes, you might provide additional data to bolster your argument, or briefly present a alternative idea that you found in one of your sources, or even list two of 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.

In all of these cases, proper citation requires that you indicate the source of any material immediately after its use in your paper. For direct quotations, the footnote (which may be a traditional footnote or the author’s name and page number in parenthesis) immediately follows the closing quotation marks; for a specific piece of information, the footnote should be placed as close as possible; for a paraphrase or a summary, the footnote may come at the end of the sentence or paragraph.

Simply listing a source in your bibliography is not adequate acknowledgment for specific use of that source in your paper. This point is extremely important and too often misunderstood by students. If you list a source in your bibliography, but do not properly place citations in the text of your paper, you can be charged with plagiarism. In Committee on Discipline hearings, students who did not set off verbatim quotations with quotation marks and footnotes, or who used ideas or information from a source without proper citation in the paper itself, sometimes argue their innocence because the source is listed in their bibliography. That puts the Committee in the difficult position of determining whether the error was a mistake based on misunderstanding the rules of citation or whether it was an intentional effort to deceive the reader. Either way, the student will be found responsible for the act of plagiarism.

For international students, it is 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; make sure you understand the University’s academic regulations and ask for assistance if you’re not sure.

The Princeton Writing Center has an extremely useful set of handouts on these topics available online at: web.princeton.edu/sites/writing/writing_center/wcwritingres.htm.

Under Examples of Plagiarism, you will find examples of plagiarism that illustrate the above rules.

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