Kevin B. Korb Lucas R. Hope Ann E. Nicholson Karl Axnick Varieties of Causal Intervention. 322-331 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3157&spage=322 2004 conf/pricai/2004 PRICAI db/conf/pricai/pricai2004.html#KorbHNA04