Question about MLA in-text citations?

To describe this the best I can: I need to do some in-text citations. The book that I am using is by a guy named San Juan Jr. However, what I am quoting from the book is part of a reprinted story by Carlos Bulosan. So, the author of the book is San Juan Jr., but this book is a collection of writings by Carlos Bulosan. How do you do an in-text citation in this case?