In addition to basic biographical information, you'll want to find books and articles by scholars, critics, and dance professionals to help you understand the choreographers life and work. These resources might be found through the library, or on the web.
For scholarly work, try Search@UW or the databases below.
Popular press, like newspapers and magazines, can also be helpful, especially for finding "primary sources" from the life of the artist-- interviews, reviews, profiles, etc. The collections linked here may be helpful.