Kees M. van Hee Rüdiger Valk Applications and Theory of Petri Nets, 29th International Conference, PETRI NETS 2008, Xi'an, China, June 23-27, 2008. Proceedings 5062 2008 978-3-540-68745-0 Petri Nets Lecture Notes in Computer Science Springer db/conf/apn/pn2008.html