@Unpublished{K-theory/0003,
  author = 	 {{Daniel R. Grayson}},
  title = 	 {{Weight filtrations via commuting automorphisms}},
  note = 	 {{Preprint, June 9, 1993, K-theory Preprint Archives, http://www.math.uiuc.edu/K-theory/0003/}}}
}