00328nam a2200133Ia 4500020001500000082001700015100001800032245002100050260005200071300002700123490003400150500000500184700000500189  a0821828770  a512bB268.AM  aBarr, Michael  aAcyclic modelsb  aProvidencebAmerican Mathematical Societyc2002  axi, 179p. Bibl. Index.  aCRM Monograph Series v v. 17  a  a