title: join index hierarchies for supporting efficient navigations in object-oriented databases. authors: jiawei han , zhaohui xie. venue: vldb. year: 1994
title: cost-driven vertical class partitioning for methods in object oriented databases. authors: chi-wai fung , kamalakar karlapalem , qing li. venue: the vldb journal -- the international journal on very large data bases. year: 2003