1. M. A. Bednarczyk. Categories of Asynchronous Transition Systems. PhD Thesis, University of Sussex, 1988.
2. J. Gischer. The Equational Theory of Pomsets. Theoretical Computer Science, n. 61, pp. 199–224, 1988.
3. J. Grabowski. On Partial Languages. Fundamenta Informaticae, n. 4, pp. 428–498, 1981.
4. M. Hennessy. Algebraic Theory of Processes. Cambridge, Massachusetts, 1988.
5. C.A.R. Hoare. Communicating Sequential Processes. Englewood Cliffs, 1985.