1. A. Shimbel, “Structure in communication nets”, Proc. Symp. on Information Networks,Polytechnic Institute of Brooklyn (1954) 119–203.
2. F.E. Hohn, S. Seshu, and D.D. Aufenkamp, “The theory of nets”, Trans. I.R.E. EC-6 (1957) 154–161.
3. B. Roy, “Transitivité et connexité”, C.R. Acad. Sci. Paris 249 (1959) 216-218.
4. R.A. Cuninghame-Green, “Process synchronisation in a steelworks - a problem of feasibility”, in: Banbury and Maitland, ed., Proc. 2nd Int. Conf. on Operational Research (English University Press,1960) 323–328.
5. B. Giffler, “Mathematical solution of production planning and scheduling problems”, IBM ASDD Technical Report (1960).