Julia Padberg Kathrin Hoffmann Magdalena Gajewsky Stepwise Introduction and Preservation of Safety Properties in Algebraic High-Level Net Systems. 249-265 2000 conf/fase/2000 FASE http://link.springer.de/link/service/series/0558/bibs/1783/17830249.htm db/conf/fase/fase2000.html#PadbergHG00