Jane Hillston Marina Ribaudo Modelling Mobility with PEPA Nets. 513-522 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3280&spage=513 2004 conf/iscis/2004 ISCIS db/conf/iscis/iscis2004.html#HillstonR04