1[4]Peterson. J.L. Petri Net Theory and The Modeling of Systems Prentice -hall [M]. Englewood Cliffs, New Jesey, 1981.
2[5]Murata. T. Modeling and Analysis of Concurrent Systems (in Handbook of Softwere Engineering [M]. C.R.Vick and C.V. Ramamooth (eds), chapter3). Van Nastrand Restrand, New york, 1984.