1. Kommunikation mit Automaten PhD dissertation;Petri,1962
2. Events and conditions;Holt,1970
3. Binary Petri-nets and Prolog for intelligent robots;Cai,1987
4. A programmable logic controller based on a high level specification tool;Courvoisier,1983
5. Programmable logic controllers and Petri nets: a comparative study;Silva,1982