Citation, Documentation of Sources

Q. The first time an author is cited in text it would appear thus: (Brown 1999, 34). The way I have been citing this author thereafter is (Brown, 56). Is that okay, or must I always put the year in the citation? If there is an author who has two works, I assume the year must always be reproduced. And if an author is cited with others, e.g., (Brown 1999; Harris 2002), should the year be put in the next time I cite only Brown?

A. Chicago’s author-date style includes the year at every citation. Although in many instances your shortening would be clear enough, it’s easier to include the date every time than to work out how to treat exceptions and confusions like the ones you raise.