The author-year notation system is required; do not use numbered notation.
For within-text citations of papers with two authors, name both.
(Murphy and Smith, 2001)
With three or more authors, use 'et al.'
(Murphy et al., 2001)
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.
(Murphy and Wong, 2001, 2001b; Murphy et al., 2001)
*For citations of multiple works by the same authors, the author names do not need to be repeated.