http://doi.acm.org/10.1145/141356.141385 db/journals/sigmod/ChatterjeeS91.html Abhirup Chatterjee Arie Segev Data Manipulation in Heterogeneous Databases. 64-68 sigmodR/20-4/P064.pdf 1991 20 SIGMOD Record 4 db/journals/sigmod/sigmod20.html#ChatterjeeS91