Albert Nymeyer Kairong Qian Heuristic Search Algorithms Based on Symbolic Data Structures. 966-979 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2903&spage=966 2003 conf/ausai/2003 Australian Conference on Artificial Intelligence db/conf/ausai/ausai2003.html#NymeyerQ03