Gerd Behrmann Patricia Bouyer Emmanuel Fleury Kim Guldstrand Larsen Static Guard Analysis in Timed Automata Verification. 254-277 2003 conf/tacas/2003 TACAS http://link.springer.de/link/service/series/0558/bibs/2619/26190254.htm db/conf/tacas/tacas2003.html#BehrmannBFL03