title: analysis of existing databases at the logical level : the dba companion project. authors: fabien de marchi , jean-marc petit , farouk toumani , stéphane lopes. venue: sigmod record. year: 2003
title: querying a multilevel database : a logical analysis. authors: fr &#233; d &#233; ric cuppens. venue: very large data bases. year: 1996