@Unpublished{K-theory/0025,
  author = 	 {{Amnon Neeman and Vladimir Retakh}},
  title = 	 {{Extension categories and their homotopy}},
  note = 	 {{Preprint, September 8, 1994, K-theory Preprint Archives, http://www.math.uiuc.edu/K-theory/0025/}}}
}