Ralf Schweimeier Michael Schroeder Fuzzy Unification and Argumentation for Well-Founded Semantics. 102-121 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2932&spage=102 2004 conf/sofsem/2004 SOFSEM db/conf/sofsem/sofsem2004.html#SchweimeierS04