Glenn Bruns Patrice Godefroid Model Checking with Multi-valued Logics. 281-293 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3142&spage=281 2004 conf/icalp/2004 ICALP db/conf/icalp/icalp2004.html#BrunsG04