00278nam a2200121Ia 4500082001900000100002300019245003700042250000900079260003000088300002800118500000500146700000500151  a518.5bU142.PD  aUllman, Jeffrey D.  aPrinciples of database systemsb  a2nd.  aNew DelhibGalgotiac1992  avii, 484p. Index. Bibl.  a  a