Herbert Weber Sabine Lembke Alexander Borusan Improving the Usability of Petri Nets with the »Petri Net Baukasten«. 54-78 2001 conf/apn/2001u Unifying Petri Nets http://link.springer.de/link/service/series/0558/bibs/2128/21280054.htm db/conf/apn/upn2001.html#WeberLB01