By Charlie Brennan, Rocky Mountain News March 16, 2005 University of Colorado investigators are looking into a letter sent last summer by professor Ward Churchill to his late wife's mother. Rhonda Kelly, 41, the sister of Leah Kelly, Churchill's late wife, said she turned over the letter to CU lawyer Louise Romero, who is working on a university investigation being led by interim Chancellor Phil DiStefano. Initially expected to be done this week, DiStefano's report - which will help CU officials decide if there is cause to fire the tenured Churchill - has been pushed back to March 28. Churchill...