Souheib Baarir Claude Dutheillet Serge Haddad Jean-Michel Ilié On the use of exact lumpability in partially symmetricalWell-formed Nets. 23-32 2005 conf/qest/2005 QEST http://doi.ieeecomputersociety.org/10.1109/QEST.2005.26 db/conf/qest/qest2005.html#BaarirDHI05