Yves Bontemps Pierre-Yves Schobbens The Complexity of Live Sequence Charts. 364-378 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3441&spage=364 2005 conf/fossacs/2005 FoSSaCS db/conf/fossacs/fossacs2005.html#BontempsS05