When your teacher asks for outside sources, s/he is not necessarily looking for an analysis of the poem you are working with. Most likely s/he wants you to bring in some outside information about Rukeyser's life or her time. Then it'll be up to you to make the links between poem and reference.
Here are a couple of quick links on the internet:
Thurston, Michael, "Biographical sketch." Modern American Poetry, retrieved January 30, 2006
Here are a few good sources that you should be able to find in any college library:
Anne F. Herzog; Janet E. Kaufman (editor). How Shall We Tell Each Other of the Poet? The Life and Writing of Muriel Rukeyser. Palgrave Macmillan. 2001. 320pp.
Louise Kertesz. The Poetic Vision of Muriel Rukeyser. Baton Rouge, LA: Louisiana State University Press. 1980.
Muriel Rukeyser. One Life. Simon & Schuster. 1957. 330pp.