db/journals/dpd/LiuHGP99.html Li-min Liu Michael Halper James Geller Yehoshua Perl Controlled Vocabularies in OODBs: Modeling Issues and Implementation. 37-65 1999 7 Distributed and Parallel Databases 1 db/journals/dpd/dpd7.html#LiuHGP99 http://kapis.www.wkap.nl/oasis.htm/186509 DPD/7/P037.pdf