Skip to main content
It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.
site header image

Biology 150: Citing Sources

Kathryn Nichols Biology 150

Citation and Reference List Guidelines

In-line Citations:

It is not necessary to list the last name of every author in the narrative. Use the following rules.

  • For one author: (Smith 2005)
  • For two authors: (Jones and Smith 2006)
  • For three or more authors: (Baker et al. 2007). Note that et does not have a period (it’s Latin for “and”), whereas al. does (it’s a contraction of the Latin alii for “others”)

If you cite multiple pieces of research to support a single statement, put the citations in chronological order and separate them with semi-colons (Smith 2005; Jones and Smith 2006; Baker et al. 2007).

Citations can be provided either by treating the author(s) as the subject of the sentence or by treating the scientific information as the subject.

  • If the authors are the subject, the year of publication is provided in parentheses. If the scientific information is the subject, the author and year of publication are both provided in parenthesis. For example (not a real scientific finding):
  • Smith (2005) discovered that consumption of chocolate caused an increase in cancer rates in mice. However, subsequent research found that this was true only under special circumstances in monkeys (Jones and Smith 2006; Baker et al. 2007).

However, it is almost always preferable to make the scientific information the subject.

  • A common mistake is introducing authors and their areas of study in general terms without mentioning their major findings. Here’s an example of a common mistake:
  • Parmenter (2010) and Chessman (2007) studied the diet of Chelodina longicollis at various latitudes and Leger (2005) and Chessman (2008) conducted a similar study on Chelodina expansa.

  • It would be much clearer to say:
  • Among carnivores, Chelodina expansa is a selective and specialized predator feeling upon highly motile prey such as crustaceans, aquatic bugs and small fish (Legler,

2005; Chessman, 2008), whereas Chelodina longicollis is reported to eat a diverse and opportunistic diet (Parmenter, 2010; Chessman, 2007).”

  • This second example is a more informative lead-in to the literature. More importantly, it enables the reader to clearly place the current work in the context of what is already known.

Citation format for the Literature Cited Section:

All citations used in the narrative must be in the Literature Cited section AND every referenced item should be used in the body text. DO NOT reference sources that are not cited in the body text.

In your Literature Cited section, list your references in alphabetical order by the last name of first author using the format below. In the Literature Cited section, always list the names and initials of ALL the authors on the paper, unless there are a very large number of authors (more than 10), in which case et al. is acceptable.

Note that a reference list is typically formatted using hanging indents to make the first author’s name easier to see.

Scientific Journal

Use this format to cite all articles published in scientific papers. Even journal articles that you find online should be cited as a printed journal article.

Note – the name of the journal is NOT the same as the database where you find a journal article!

Last name(s) and initials of author(s). Year of publication. Name of article. Name of journal. Volume(Issue): pages.

Examples:

Andersson, S. 2012. Does inbreeding promote evolutionary reduction of flower size?

Experimental evidence from Crepis tectorum (Asteraceae). American Journal of Botany 99:

1388-1398.

Arntz, A.M., and L.F. Delph. 2001. Pattern and process: evidence for the evolution of photosynthetic

                traits in natural populations. Oecologia 127(4): 455-467.

Book

Use this format to cite books. As with journal articles, even books that you find online as a digital book should be cited as a printed source.

Last name(s) and initials of author(s). Year of publication. Title (with edition number if appropriate).

Publisher, City, State or Country.

Example:

Stebbins, G.L. 1974. Flowering Plants: Evolution above the Species Level. Harvard University

Press, Cambridge, MA.

Book chapter in an edited volume

Use this format to cite book chapters; this includes entries in encyclopedia-style books as well as more traditional books.

Last name(s) and initials of chapter author(s). Year of publication. Chapter title. Page numbers in Book editor(s) and initial(s) (Eds.) Book title. Publisher, City, State or Country.

Example:

Eckert, C. G., K. E. Samis, and S. Dart. 2006. Reproductive assurance and the evolution of uniparental

reproduction in flowering plants. Pp. 183-203 in L. D. Harder, and S. C. Barrett (Eds.) Ecology and

evolution of flowers. Oxford University Press, Oxford, UK.

Web sites

Web site sources should be used sparingly and with great caution. Make sure any web-based sources are exceptionally reliable before using them!

Last name(s) and initials of author(s). Year of latest online update. Title. URL Accessed date.

Example:

Becklehimer, J. 1994. How do you cite URLs in a bibliography?

http://www.nr/ssc.navy.mil/meta/bibliography.html. Accessed February 6, 2015.

Important note: web sites without an author or a date of publication are normally not suitable for use in any kind of science report or paper. However, if you do need to cite such articles, use n.a. for “no author” and “n.d.” for no date. If there is no author, cite the title of the article first, as follows

Example:

Baker, C.D. (n.d.) Web sites without authors or publication dates are not to be trusted. URL. Accessed October 30, 2015.

Web sites without authors or publication dates are not to be trusted.