Serge Haddad Jean-Michel Ilié Mohamed Taghelit Belhassen Zouari Symbolic Reachability Graph and Partial Symmetries. 238-257 1995 conf/apn/1995 Application and Theory of Petri Nets db/conf/apn/apn95.html#HaddadITZ95 http://dx.doi.org/10.1007/3-540-60029-9_43