How do I cite multiple sources by the same author in APA Style?
In APA Style, if you use multiple sources from the same author that have different publication years, the different publication years are sufficient to distinguish the citations.
To cite multiple sources with the same publication year in an APA in-text citation, include the author name and date as usual, and add a lowercase letter to the end of the publication year (Perkins, 2004a; Perkins, 2004b).