00334nam a2200133Ia 4500082002000000100002100020245003100041250000900072260004900081300002000130490004000150500000500190700000500195  a511.3bSa121.DU  aSacks, Gerald E.  aDegrees of unsolvabilityb  a2nd.  aNew JerseybPrinceton University Pressc1966  aix, 174p. Bibl.  aAnnals of Mathematics studies v 55  a  a