In-text citations to books or articles by a single author generally include the author's last name and the publication date of the work you're citing, enclosed by parentheses:
The evidence for this hypothesis is suspect (Burns 1969:32).
If the author's last name is clear from your sentence, then it does not need to be included in the in-text citation:
Tonkinson (1978:27) notes that the Aborigines of the Western Desert...
What if you refer to two different books or articles by the same author? How do you let the reader know that two different publications are being cited? You simply use the year of publication to distinguish them. They will be listed chronologically under the author's name in the reference list.
This population will frequently be found in establishments which serve caffeinated beverages (Stone 2006:23).
Ritual imbibing of caffeinated beverages among members of this tribe has been observed to precede a rise in humorous conversations (Stone 2012:589).
What if they were published the same year? Then you can add lower case letters after the publication date.
Coffee is tasty (Stone 2006a:13).
Coffee may induce overly ambitious planning for the weekend (Stone 2006b:65).
