When you are citing two different sources that share the same author and year of publication, assign lowercase letters after the year of publication (a, b, c, etc.). Assign these letters according to which title comes first alphabetically. Use these letters in both in-text citations and the Reference list.
Paraphrasing content from first source by this author (Daristotle, 2015a). "Now I am quoting from the second source by the same author" (Daristotle, 2015b, p. 50).
Example Reference list entries:
Daristotle, J. (2015a). Name of first article. Made Up Journal, 26(39), 18-19.
Daristotle, J. (2015b). Title of second article. Another Made Up Journal, 35(1), 48-55.