Chien-Liang Chen Suey Wang Hsu-Chun Yen Reachability Analysis of Variants of Communication-Free Petri Nets. 377-388 2009 92-D IEICE Transactions 3 http://search.ieice.org/bin/summary.php?id=e92-d_3_377&category=D&year=2009&lang=E&abst= db/journals/ieicet/ieicet92d.html#ChenWY09