Olga Fengler Wolfgang Fengler Vesselka Duridanova Extending the Modeling Efficiency of the UML Activity Diagram for the Design of Distributed Systems. 51-62 http://link.springer.de/link/service/series/0558/bibs/2346/23460051.htm 2002 conf/iics/2002 IICS db/conf/iics/iics2002.html#FenglerFD02