00331nam a2200133Ia 4500082001700000100001900017245002700036260003400063300001600097490003900113500003500152500000500187700000500192  a512bP495.RS  aPetrich, Mario  aRings and semigroupsb  aBerlinbSpringer-Verlagc1974  aviii, 182p.  aLecture notes in Mathematicsv 380  a"Appendix by Richard Wiegandt"  a  a