Cristian Mahulea Antonio Ramírez-Treviño Laura Recalde Manuel Silva Steady-State Control Reference and Token Conservation Laws in Continuous Petri Net Systems. 307-320 2008 5 IEEE T. Automation Science and Engineering 2 http://dx.doi.org/10.1109/TASE.2007.893504 db/journals/tase/tase5.html#MahuleaRRS08