1983

Gregor Engels, Hans-Dietrich Ehrich, Udo Pletat: An Operational Semantics for Specifications of Abstract Data Types with Error Handling. In Acta Informatica, vol. 9, no. 3, pp. 235-254. Springer (Berlin/Heidelberg) (1983) 

Gregor Engels, Rupert Gall, Wilhelm Schäfer: Software Specification Using Graph Grammars. InComputing, vol. 31, no. 4, pp. 317-346. Springer (Berlin/Heidelberg) (1983) 

Manfred Nagl, Gregor Engels, Rupert Gall, Wilhelm Schäfer: Software Specification by Graph Grammars. In H. Ehrig, M. Nagl, G. Rozenberg (eds.): Proceedings of the 2nd International Workshop on Graph-Grammars and Their Application to Computer Science, Osnabrück (Germany). Springer (Berlin/Heidelberg), LNCS, pp. 267-287 (1983)