APA journals use the author-date method of citation.
Surname of the author (not including suffix such as Jr.) and the year of the publication are inserted at the appropriate point.
One Work by One Author
Example:
Quimby (2000) compared monorail systems
In a recent study of monorail systems (Quimby, 2000)
In 2000 Quimby compared monorail systems
One Work by Multiple Authors
When a work has two authors, always cite both names every time the reference occurs in text.
Example:
As Smithers and Skinner (1993) demonstrated
as has been shown (Nahasapeemapetilon & Ormand, 1989)
When a work has three, four, or five authors...
Cite all the authors the first time the reference occurs.
In subsequence citations, include only the surname of the first author followed by et al. (including the period)
Cite the year if it is the first citation of the reference within a paragraph.
Example:
Hibbert, Rivera, Monroe, Foster, Zweig, and Colossus (1994) found [Use as first citation in the text]
Hibbert et al. (1994) found [Use as subsequent first citation per paragraph thereafter.]
Hibbert et al. found [Omit year from subsequent citation after first citation within a paragraph.]
When a work has six or more authors, cite only the surname of the first author followed by et al.
Example:
Wiggum et al. (1983) found [First in a paragraph citation]
Wiggum et al. also found [Omit the year after the first citation in the same paragraph]
Exceptions in Multiple Authors...
If two references with the same year shorten to the same form, cite the surnames of the first authors and of as many of the subsequent authors as necessary to distinguish the two references, followed by a comma and et al.
Example:
If there are two resources with the author:
Meyers, Bobbins, & Powers, 1994, and Meyers, Powers, Bobbins, & Groening, 1994 both shorten to Meyers et al., 1994
Bradley, Ramirez, and Soo (1994) and Bradley, Soo, et al. (1994)
No Author or Anonymous Author
Cite the text the word Anonymous followed by a comma and the date.
Example:
(Anonymous, 1998)
Other Examples
Authors with same surname - S. Duff (1959) and R. Duff (1989) also found
Two or more works by the same author(s) - Past research (Jones & Muntz, 1981, 1983)
Works by same authors with same pub. date - Several studies (Brockman & Pie, 1978a, 1979b)
Works by different authors are listed in the same parentheses in alphabetical order - Several studies (Frink & Stu, 1979; Moleman, 1978)
Specific part of a source - (Pennycandy, 1980, chap. 35)
For letters, conversations, etc. (Cite only in text.) - S. Stanky (personal communication, November 1, 2000)
Information was gathered from Publication manual of the American Psychological Association (5th Ed)