Citation, Documentation of Sources
Q. In the author-date format, are multiple references divided by commas or semicolons?
A. Use semicolons to separate references. If there are also locators, put a comma between the year and locator.
(Armstrong and Malacinski 1989; Beigl 1989; Pickett and White 1985)
(Wong 1999, 328; 2000, 475; García 1998, 67)