title: dblearn : a system prototype for knowledge discovery in relational databases. authors: yue huang , yandong cai , yongjian fu , nick cercone , jiawei han. venue: sigmod conference. year: 1994
title: schemasql - a language for interoperability in relational multi-database systems. authors: laks v. s. lakshmanan , fereidoon sadri , iyer n. subramanian. venue: very large data bases. year: 1996