Enric Pastor Marco A. Peña Efficient Hybrid Reachability Analysis for Asynchronous Concurrent Systems. 378-393 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2860&spage=378 2003 conf/charme/2003 CHARME db/conf/charme/charme2003.html#PastorP03