00331nam a2200121Ia 4500008004100000020001800041082000800059100001700067245005100084260005000135300000800185650001600193220919s9999    xx            000 0 und d  a9780821820025  bGRA  aGRAG, HJORTH 0aCLASSIFICATION AND ORBIT EQUIVALENCE RELATIONS  bAMERICAN MATHEMATICAL SOCIETY, AMERICANc2000  a195  aMathematics