Authors and multiple authors are handled in the same way for all references.
(There are some exceptions which are not shown here).
Refer to the 7th edition, Concise Guide to APA Style: the official APA style guide for students - Inside cover or chapter 8, pg. 181, 8.10
Please review Chapter 8 for additional information on in-text citation
All Author formats:
Last name, First. Middle Initial(s). (there won't always be a middle initial).
One Author:
Smith, J.C. (2012).
In-text: (ex1) (Smith, 2012); (ex2) Smith (2012) discovered...; (ex3) In 2012, Smith discussed in her study of...
Two Authors:
Smith, J.C. & Jones, A.T. (2012).
In-text: (ex1) (Smith & Jones, 2012); (ex2) Smith and Jones (2012) deduced that...; (ex3) In 2012, Smith and Jones produced a study...
Three to Twenty Authors (list all authors):
Smith, J.C., Jones, A.T., Parker, A., Trooper, B., Johnson, K.J., Kalun, P., & Daigle, R. (2012).
In-text: (ex1) (Smith et al., 2012); (ex2) Smith et al. (2012) discovered...
Twenty-one or More Authors (list all 21 authors, then the "..." and last author):
Smith, J.C., Jones, A.T., Parker, A., Trooper, B., Johnson, K.J., Kalun, P., Jones, A.T., Parker, A., Trooper, B., Johnson, K.J., Kalun, P, Jones, A.T., Parker, A., Trooper, B., Johnson, K.J., Kalun, P, Jones, A.T., Parker, A., Trooper, B., Johnson, K.J., Kalun, P . . .Miller, S.C. (2012)
In-text: (ex1) (Smith et al., 2012); (ex2) Smith et al. (2012) discovered...