1. Dijkstra, E.W.: Guarded Commands, Nondeterminacy, and Formal Derivation of Programs, CACM Vol. 18, No. 8, acm Press (1975), S. 453–457
2. Ehrig H., Kreowski H.-J., Rozenberg G. (eds.): Proc. 4th Int. Workshop on Graph-Grammars and Their Application to Computer Science; (published in) LNCS, Springer Verlag (1991)
3. Engels G.: Graphen als zentrale Datenstrukturen in einer Software-Entwicklungsumgebung; Ph.D. Thesis, VDI-Verlag (1986)
4. Engels G., Janning Th., Schäfer W.: A Highly Integrated Tool Set for Program Development Support, Proc. ACM SIGSMALL Conf., acm Press(1988), pp.1–10
5. Engels G., Schäfer W.: Graph Grammar Engineering: A Method Used for the Development of an Integrated Programming Support Environment; in Ehrig et al.(Eds.): Proc. TAPSOFT'85, LNCS 186; Berlin: Springer-Verlag, pp. 179–193