Magdalena Gajewsky Hartmut Ehrig The »Petri Net Baukasten«: An Overview. 26-53 2001 conf/apn/2001u Unifying Petri Nets http://link.springer.de/link/service/series/0558/bibs/2128/21280026.htm db/conf/apn/upn2001.html#GajewskyE01