00321nam a2200121Ia 4500008004100000040001600041041001200057082001700069100001900086245003000105260004800135300001600183230917s9999||||xx |||||||||||||| ||und||  e83186aMAIN  aEnglish  a512.22 H888N  aHumphreys, J F 0aNumbers, groups and codes  aCambridgebCambridge University Pressc1989  axvi, 288 p.