Yuri Karpov Dmitry Sotnikov Interval Approach to Parallel Timed Systems Verification. 100-116 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2763&spage=100 2003 conf/pact/2003 PaCT db/conf/pact/pact2003.html#KarpovS03