"Ethics, copyright laws, and courtesy to readers require authors to identify the sources of direct quotations and of any facts or opinions not generally known or easily checked."--
Chicago Manual of Style, 15th edition (Chicago: Chicago Univ. Press), p. 594
Why cite sources? Whenever you quote or base your ideas on another person's work, you must document the source you used. Even when you do not quote directly from another work, if reading that source contributed to the ideas presented in your paper, you must give the authors proper credit.
Citations allow readers to locate and further explore the sources you consulted, show the depth and scope of your research, and give credit to authors for their ideas. Citations provide evidence for your arguments and add credibility to your work by demonstrating that you have sought out and considered a variety of resources. In written academic work, citing sources is standard practice and shows that you are responding to this person, agreeing with that person, and adding something of your own. Think of documenting your sources as providing a trail for your reader to follow to see the research you performed and discover what led you to your original contribution.
How do you cite sources? The means to identify sources is to provide citations within your text linking appropriate passages to relevant resources consulted or quoted. This can be done through in-text parenthetic notes, footnotes, or endnotes. In addition, a bibliography or list of works cited, is almost always placed at the end of your paper. The citation system and format you use will be determined by the citation style you choose.
Below are links to guides for the three major styles used for most academic papers or research in the humanities, social sciences, and some scientific disciplines:
APA Style Guide (Purdue) - From the American Psychological Association. Often preferred in the fields of psychology and many other social sciences.
MLA Style Guide (Purdue) - From the Modern Language Association of America. Often preferred in the fields of literature, arts, humanities, and in some other disciplines.
Turabian & Chicago Styles Guide - From the work of Kate Turabian at the University of Chicago and the University of Chicago Press. Often preferred in history and many other disciplines.
How do you choose a style? Ask your instructor which style sheet he or she wishes you to use and if there are other special formatting instructions you should follow.
Where do I find the most authoritative information about these styles? If you have questions or citations not covered by the Library's guides, please consult one of the following official style manuals. If you consult other, less official manuals or online style guides that purport to explain these style, please be aware that these sometimes contain errors which conflict with the official guides:
Publication Manual of the American Psychological Association. 6th ed. Washington, DC: American Psychological Association, 2010 (call number: BF76.7.P83 2010, multiple libraries). Official APA style guide.
MLA Handbook for Writers of Research Papers. 7th ed. New York: Modern Language Association of America, 2009 (call number: LB2369.G53 2009, multiple libraries). A somewhat simplified guide, adequate for undergraduate and most other research papers.
MLA Style Manual and Guide to Scholarly Publishing. 3rd ed. New York: Modern Language Association of America, 2008 (call number: PN147.G444 2008, multiple libraries). For graduate students, scholars, and professional writers (more depth on copyright, legal issues, and writing theses, dissertations, and scholarly publishing).
Turabian, Kate L. A Manual for Writers of Term Papers, Theses, and Dissertations, 6th edition. Chicago: University of Chicago Press, 1996 (call number: LB2369.T8 1996, multiple libraries).
The Chicago Manual of Style. 15th ed. Chicago: University of Chicago Press, 2003 (call number: Z253.U69 2003, multiple libraries).