The author–year notation system is required; do not use
numbered notation. For within-text citations of papers with two authors, name both.
With three or more authors, use ‘et al.’ For two or more articles using the same
within-text citation, add a distinguishing lowercase letter to the year in both
the text and references list. Separate citations with a semicolon. For citations
of multiple works by the same authors, the author names do not need to be repeated.
Examples:
(Murphy, 2001)
(Murphy, 2001; Murphy and Smith, 2001; Murphy et al., 2001)
(Murphy, 2001; Murphy and Wong, 2001, 2001b; Murphy et al., 2001)
(Murphy, 2001; Murphy et al., 2001, 2002; Murphy and Davis, 2002)