1. R.Milner, A Calculus of Communicating Systems, Lect.Not.Comp.Sc. 92, Springer, 1980
2. W.Brauer ed., Net Theory and Applications, Lect.Not.Comp.Sc. 84, Springer, 1980
3. H.J.Genrich, P.S.Thiagarajan, Bipolar Synchronization Systems, Lect.Not. Comp.Sc.85, Springer, 1980
4. C.André, Behaviour of a Place-Transition net on a subset of transitions, Inf.Fach.Berichte 52, Springer, 1982
5. C.André, Use of Behaviour Equivalence in Piece-Transition nets analysis, ibidem