The best and most important thing you can do is read and re-read the work very carefully. Often these points of interest provide beginnings of good thoughts for essays. Your teacher expects you to explore the work on your own, and there is no better way to do this than to read and re-read Cather slowly and appreciatively.
Students often ask for specific information or articles on the Web.
All that I know of is collected here on this site, but there is very little available. Your best resource is still your library , whether at your school or in your community. Even if your library does not have the materials you are seeking, they are often able to order them on loan from other libraries. Librarians are very helpful about this. The journal which focuses exclusively on Willa Cather's life and work is called The Willa Cather Pioneer Memorial Journal .