[stylist] question about siting sources

[Vejas via stylist]

Hi All,
I have a question about siting sources.  How should you site the 
author's last name if you have 2 sources by her?
For English, I'm writing about how Amy Tan's life and one of her 
books connect.  I found a memoir by Amy Tan herself which I have 
found very helpful, but how do I make it so that they are clearly 
different? If I put Tan 77, nobody's going to know if I mean page 
77 in her fiction book or page 77 in her memoir.
Thanks,
Vejas