@Unpublished{K-theory/1003,
  author = 	 {{Daniel Quillen}},
  title = 	 {{Letter to Segal, July 25, 1972}},
  note = 	 {{Preprint, August 8, 2011, K-theory Preprint Archives, http://www.math.uiuc.edu/K-theory/1003/}}}
}