Oliver Kopp Daniel Martin Daniel Wutke Frank Leymann The Difference Between Graph-Based and Block-Structured Business Process Modelling Languages 3-13 2009 4 Enterprise Modelling and Information Systems Architectures 1 http://www.wi-inf.uni-duisburg-essen.de/MobisPortal/index.php?lang=en&&groupId=1&&contentType=JournalMembers&issue=6&showAbstract=34 db/journals/emisaij/emisaij4.html#KoppMWL09