@Unpublished{K-theory/0077,
  author = 	 {{Manuel Cardenas and Erik K. Pedersen}},
  title = 	 {{On the Karoubi filtration of a category}},
  note = 	 {{Preprint, June 20, 1995, K-theory Preprint Archives, http://www.math.uiuc.edu/K-theory/0077/}}}
}