An essential component of a research paper, in-text citations are a way of acknowledging the ideas of the author(s) of a particular work.
Each source that appears as an in-text citation should have a corresponding detailed entry in the References list at the end of the paper. Including the required elements in every citation allows other researchers to easily track the references used in a paper and locate those resources themselves.
There are three pieces of information that should be included in a citation after quoting another writer’s work: the author’s last name, the year of publication, and the page number(s) of the quoted material, all of which are separated by commas. The page number should follow a lower-case letter 'p' and a period.
- Basic structure: (Author, Year of Publication, p. 142)
- Example: (Kutner, 2003, p. 451) 
If the quoted material was taken from more than one page, use two lower-case letter 'p' s.
- Basic structure: (Author, Year, of Publication, pp. 194-196)
- Example: (Kutner, 2003, pp. 451-452) 
How should multiple authors of a single source be cited?
There are a few guidelines to follow when citing multiple authors for a single source. Separate the names of the source’s authors by using commas. Depending on the location and instance of the citation, an ampersand(&), the word and, or the term et al. may also need to be used.
When should an ampersand be used?
Ampersands (&) should only be used in parenthetical in-text citations. An ampersand separates the last and second to last author of a cited work.
- Example: Research has demonstrated that “synesthesia appears quite stable over time, and synesthetes are typically surprised to discover that other people do not share their experiences” (Niccolai, Jennes, Stoerig, & Van Leeuwen, 2012, p. 81). 
When should the word and be used?
The word and should only be used in a sentence or paragraph; do not use it in a parenthetical in-text citation. The last and second to last author of a cited work are separated by the word and.
- Example: Niccolai, Jennes, Stoerig, and Van Leeuwen (2012) observed that “synesthesia appears quite stable over time, and synesthetes are typically surprised to discover that other people do not share their experiences” (p. 81). 
When should the term et al. be used?
When citing a single work with many authors, you may need to substitute some of the authors’ names with the term et al. The termet al. should not be italicized in your paper, and a period should be placed after the word al as it is an abbreviated term. Follow these guidelines regarding the usage of et al.:
Use et al.:
- The first time and every time you cite a source with at least six authors.
- Example: The in-text citation of Zoonoses: Infectious diseases transmissible from animals to humans, a book authored by Krauss, Weber, Appel, Enders, Isenberg, Schiefer, Slenczka, von Graevenitz, and Zahner, would appear as follows: 
(Krauss et al., 2003, p. 91)
- As Krauss et al. (2003) observed, …
- Every following time (after the first instance) that you cite a source with at least three authors.
- Example: Citing the article “Modality and variability of synesthetic experience” by Niccolai, Jennes, Stoerig, & Van Leeuwen would appear as follows: 
The first instance: (Niccolai, Jennes, Stoerig, & Van Leeuwen, 2012, p. 81)
- Every following instance: (Niccolai et al., 2012)
Avoid using et al.:
- The first time you cite a source with up to five authors.
- Instead, list all of the authors at their first mentioning.
- To cite a work that only has two authors.
- Instead, always list the two authors’ names in every citation (separated by either an ampersand or the word and, depending on the location)
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