Anthony Hunter Rupert Summerton Propositional Fusion Rules. 502-514 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2711&spage=502 2003 conf/ecsqaru/2003 ECSQARU db/conf/ecsqaru/ecsqaru2003.html#HungerS03