When mentioning the author in the text of your sentence, provide the page number(s) of the reference at the end of the sentence in parentheses. Example: Tannen has argued this point (178-85). or It may be true, as Robertson maintains, that "in appreciation of medieval art the attitude of the observer..." (136).
When not mentioning the author in the text of your sentence, provide the author and the page number(s) at the end of the sentence in parentheses. Example: This point has already been argued (Tannen 178-85). or It may be true that "in the appreciation of medieval art the attitude of the observer..." (Robertson 136).