A source with three to five authors

In all citations after the first, use the first author's name followed by et al.

First citation: (Baldwin, Bevan, & Beshalke, 2000)

Subsequent citation: (Baldwin et al., 2000)

A source with six or more authors

Use the first author's name followed by et al. in all citations

6 authors: (Utley et al., 2001)

7 authors: (Yawn et al., 2001)

[Note: In the reference list, use of et al. begins with 7-author references.]

Sources with two or more six-author groups with same first surname

If two or more six-author groups shorten to the same surname, cite the surnames of as many subsequent authors as needed to distinguish references.

(Baldwin, Utley et al., 2001)

(Baldwin, Bevan et al., 2000)