If you are citing a source that has multiple authors, follow these basic steps.
Always cite both authors' names in-text everytime you reference them. Example: Johnson and Smith (2009) found...
Provide all the authors' last names when you first refer to a document with 3-5 authors. Only list the first author with the Latin abbreviation "et al." for any subsequent references.
Jones, Chavez, Jackson, and Chen (2010) duplicated...
Jones et al. (2010) further described...
6 or More Authors:
If a document has six or more authors, simply provide the last name of the first author with "et al." from the first citation to the last.
Thomas et al. (2007) likened abnormal psychology to...
... distractions (Thomas et al., 2007).
Important Note: If you have two or more documents that look the same when shortened, please follow the guidelines set out in the Authors and Dates Matching section.
APA Manual p.175, Section 6.12
Sagarin, B. J., & Lawler-Sagarin, K. A. (2005). Critically evaluating competing theories: An exercise based on the Kitty Genovese murder. Teaching of Psychology, 32(3), 167–169. https://doi.org/10.1207/s15328023top3203_8
What is a DOI?
Some library databases, such as PsycARTICLES and PsycINFO, list a Digital Object Identifier (DOI) for individual articles. A DOI is a unique identifying number for an article. In the database record for an article, you will see an element that looks like this, which you should include at the end of your APA reference, preceded by "https://doi.org/":
This link will allow a reader to link to doi.org for more information about the article.
However, the APA Style Guide to Electronic References (2012, p. 5) notes that it is still acceptable to use the older style of DOI format in a citation, for example:
Amidzic, O., Riehle, H. J., & Elbert, T. (2006). Toward a psychophysiology of expertise: Focal magnetic gamma bursts as a signature of memory chunks and the aptitude of chess players. Journal of Psychophysiology, 20(4), 253-258. doi:10.1027/0269-8803.20.4.253