Environment and Society in a Changing World

Citation and Reference Style


Citation and Reference Style


We expect that the text and graphics you submit as part of your assignments are original. We use the plagiarism detection service to assure the originality of assignments. You may build upon ideas, words and illustrations produced by others, but you must acknowledge such contributions formally. Unacknowledged contributions are considered to be plagiarized. This guide explains when and how you should acknowledge contributions of others to your own work.

Different disciplines adopt different standards for citations and references. Moreover, almost every professional publication enforces its own variation on the standard styles. The most widely used styles include:

  • APA - Used in psychology, education, and other social sciences;
  • MLA - Used in literature, arts, and humanities;
  • AMA - Used in medicine, health, and biological sciences;
  • Turabian - Designed for college students to use with all subjects;
  • Chicago - Used with all subjects in non-academic publications like books, magazines, and newspapers.

In this course, we recommend that you use the APA style, documented at the Purdue Online Writing Lab. Recognizing that many variations of APA style are in use, we do not enforce the Purdue style strictly. However, we do expect two things:

  1. Whenever you include text, a graphic, or an idea that is not your own, acknowledge the contribution in such a way that enables readers to find the original source; and
  2. Consistently apply one style of citations and references throughout all your assignments.

In focus: Text ("In-Line") Citations

Quotations: Whenever you include in your writing a direct quotation from another person's written or verbal communications, you must cite your source properly. List the author(s), date of publication and page number in parentheses at the end of the sentence with the quotation.

Text Citations Example #1, A Quotation: Does geographic information science merit recognition as a distinct field? Some claim that the distinction is justified, but only if "we...first establish that spatial, or rather, geographical, data are unique" (Goodchild, 1992, p. 32)

Important: Complete references corresponding to each citation should appear in the Reference List at the end of every assignment report.

Paraphrasing: Most often you will cite ideas rather than quotations. Your ability to paraphrase and build upon the work of others constitutes more convincing evidence of your professional and intellectual development than your ability to assemble series of quotations. The Student Judicial Services office at the University of Texas has published the following excellent explanation of proper paraphrasing (note the extended quotation is set apart as a "block quote"):

Like a direct quotation, a paraphrase is the use of another's ideas to enhance one's own work. For this reason, a paraphrase, just like a quotation, must be cited. In a paraphrase, however, the author rewrites in his or her own words the ideas taken from the source. Therefore, a paraphrase is not set within quotation marks. So, while the ideas may be borrowed, the borrower's writing must be entirely original; merely changing a few words or rearranging words or sentences is not paraphrasing. Even if properly cited, a paraphrase that is too similar to the writing of the original is plagiarized. 

Good writers often signal paraphrases through clauses such as "Werner Sollors, in Beyond Ethnicity, argues that..." Such constructions avoid excessive reliance on quotations, which can clog writing, and demonstrate that the writer has thoroughly digested the source author's argument. A full citation, of course, is still required. When done properly, a paraphrase is usually much more concise than the original and always has a different sentence structure and word choice. Yet no matter how different from the original, a paraphrase must always be cited, because its content is not original to the author of the paraphrase (Student Judicial Services Center, University of Texas, no date).

Text Citations Example #2, A Paraphrased Idea: Geographic information science ought to be considered a distinct field because georeferenced data embody unique characteristics (Goodchild, 1992).


At the end of your report, you must list the full bibliographic citations of the works you have used. The list should be alphabetized and references should include the following:

  • Author(s) name(s)
  • Publication date
  • Publication title
  • Editors (if publication appears in an edited collection)
  • Edition title and number (if applicable)
  • URL (if applicable)
  • Date retrieved (for web publications)
  • City, State, and Name of publisher (if applicable)
  • Page number (for quotations from printed sources)

Type of source and reference example

Basic book

Author, A. A. (Year of publication). Title of work: Subtitle. Location: Publisher.

Example: Chrisman, N. (1997). Exploring geographic information systems. New York: John Wiley & Sons, Inc.

Chapter of an Edited Book

Author, A. A., & Author, B. B. (Year of publication). Title of chapter. In A. Editor & B. Editor (Eds.), Title of book (pages of chapter). Location: Publisher.

Example: Cowen, D. J., & Jensen, J. R. (1998). Extraction and Modeling of Urban Attributes Using Remote Sensing Technology. In D. Liverman, E. F. Moran, R. R. Rindfuss & P. C. Stern (Eds.), People and Pixels: Linking Remote Sensing and Social Science (pp. 164 – 188). Washington, D. C.: National Academy Press, National Research Council.

Edition other than first

Author, A. A. (Year of publication). Title of work: Subtitle. (# ed.). Location: Publisher.

Example: Lillesand, T., & Kiefer, R. (1994). Remote sensing and image interpretation (3rd ed.). New York, NY: John Wiley and Sons.

Article in a Periodical

Author, A. A., Author, B. B., & Author, C. C. (Year). Title of article. Title of Periodical, volume number (issue number), pages.

Example: Goodchild, M. (1992). Geographical information science. International Journal of Geographic Information Systems 6:1, 31-45.

Electronic Source

Author, A. A., & Author, B. B. (Date of publication). Title of document. Retrieved month date, year, from URL.

Example: (n. d.). Welcome to TopoZone. Retrieved February 4, 2007, from  (Links to an external site.)

(In this particular case "n.d." stands for "no date of publication available"--which is sometimes the case for online sources.)

Article from an Online Periodical

Author, A. A., & Author, B. B. (Date of publication). Title of article. Title of journal, volume number (issue number if available). Retrieved month day, year, from

Example: Bernstein, M. (2002). 10 tips on writing the living Web. A List Apart: For People Who Make Web sites, 149. Retrieved May 2, 2006 from is external)

Topographic Map Author

“Sheet title” (date). [format]. Edition. Scale. Series, sheet number. Place of publication, Date.

Example: United States Geologic Survey. "Bellefonte, PA Quadrangle" (1971). [map]. 1:24 000. 7.5 minute series. Washington, D.C.:USGS.