1. G. Boudol, I. Castelani, A non Interleaving Semantics for CCS based on Proved Transitions, Fundamenta Informatica 11(4) 1988.
2. E. Best, R. Deviller Sequential and Concurrent Behavior in Petri Net Theory. TCS Vol 50
3. P. Degano, R. DeNicola, U. Montanari, A new operational semantics for CCS based on condition event systems. Nota Interna B4-42, Dept. of CS, Univ. Pisa 1986.
4. U. Goltz, W. Reisig, The non Sequential Behaviour of Petri Nets, Information and Control 57 Nos 2–3 1983.
5. Hoare, C.A.R., Communicating sequential processes, Prentice Hall International, 1985.