00275nam a2200121Ia 4500082001700000100001700017245003900034260003300073300001300106490002400119500000500143700000500148  a512bH861.IS  aHowie, J. M.  aIntroduction to semigroup theoryb  aLondonbAcademic Pressc1976  ax, 272p.  aL. M. S. monographs  a  a