If there are two different sources by the same author in the same year, put the sources in alphabetical order and add a lower-case letter after the year (this will correspond with the matching reference).
Parenthetical Citation Example
(Jones, 2001a, p. 106)
(Jones, 2001b, p. 13)
Narrative Citation Example
Jones (2001a) … (p. 106)
Jones (2001b) … (p. 13)
Corresponding References Example
Jones, A. (2001a). This book is not real. Penguin Press.
Jones, A. (2001b). Another fake book for the sake of an example. Oxford University Press.