Ugo Dal Lago Angelo Montanari Gabriele Puppis Towards Compact and Tractable Automaten-Based Representations of Time Granularities. 72-85 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2841&spage=72 2003 conf/ictcs/2003 ICTCS db/conf/ictcs/ictcs2003.html#LagoMP03