title: storing and querying ordered xml using a relational database system. authors: kevin s. beyer , jayavel shanmugasundaram , chun zhang , igor tatarinov , stratis viglas , eugene j. shekita. venue: sigmod conference. year: 2002
title: unisql/x unified relational and object-oriented database system. authors: won kim. venue: international conference on management of data. year: 1994