Pawel Placek Dimitri Theodoratos Stefanos Souldatos Theodore Dalamagas Timos K. Sellis A heuristic approach for checking containment of generalized tree-pattern queries. 551-560 2008 CIKM http://doi.acm.org/10.1145/1458082.1458155 conf/cikm/2008 db/conf/cikm/cikm2008.html#PlacekTSDS08