Samik Basu Diptikalyan Saha Yow-Jian Lin Scott A. Smolka Generation of All Counter-Examples for Push-Down Systems. 79-94 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2767&spage=79 2003 conf/forte/2003 FORTE db/conf/forte/forte2003.html#BasuSLS03