Wolfgang Weitz Workflow Modeling for Internet-Based Commerce: An Approach Based on High-Level Petri Nets. 166-178 http://link.springer.de/link/service/series/0558/bibs/1402/14020166.htm 1998 conf/ifip/1998trec Trends in Distributed Systems for Electronic Commerce db/conf/ifip/trec1998.html#Weitz98