@Unpublished{K-theory/0833,
  author = 	 {{Efton Park and Jody Trout}},
  title = 	 {{K_0-theory of n-potents in rings and algebras}},
  note = 	 {{Preprint, April 7, 2007, K-theory Preprint Archives, http://www.math.uiuc.edu/K-theory/0833/}}}
}