00288nam a2200121Ia 4500082001900000100001800019245002800037260003600065300001300101490004200114500000500156700000500161  a511.6bP429.CM  aPercus, J. K.  aCombinatorial methodsb  aNew YorkbSpringer-Verlagc1971  ax, 195p.  aApplied Mathematical Sciences v v. 4  a  a