Semra Dogandag Paolo Ferraris Vladimir Lifschitz Almost Definite Causal Theories. 74-86 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2923&spage=74 2004 conf/lpnmr/2004 LPNMR db/conf/lpnmr/lpnmr2004.html#DogandagFL04