title: garbage collection in object-oriented databases using transactional cyclic reference counting. authors: s. sudarshan , prasan roy , abraham silberschatz , srinivas ashwin , s. seshadri. venue: vldb j.. year: 1998
title: optimizing queries with universal quantification in object-oriented and object-relational databases. authors: jens clau &#223; en , alfons kemper , guido moerkotte , klaus peithner. venue: very large data bases. year: 1997