Manfred Jaeger A Representation Theorem and Applications. 50-61 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2711&spage=50 2003 conf/ecsqaru/2003 ECSQARU db/conf/ecsqaru/ecsqaru2003.html#Jaeger03