Michael M. David ANSI SQL Hierarchical Processing Can Fully Integrate Native XML. 41-46 2003 32 SIGMOD Record 1 http://doi.acm.org/10.1145/640990.640996 http://www.acm.org/sigmod/record/issues/0303/7.sql-hier-proc.pdf db/journals/sigmod/sigmod32.html#David03