Giacomo Bucci Andrea Fedeli Luigi Sassoli Enrico Vicario Modeling Flexible Real Time Systems with Preemptive Time Petri Nets. 279-286 2003 conf/ecrts/2003 ECRTS http://csdl.computer.org/comp/proceedings/ecrts/2003/1936/00/19360279abs.htm db/conf/ecrts/ecrts2003.html#BucciFSV03