M. Nagl, G. Engels, R. Gall, and W. Schäfer, “Software Specification by Graph Grammars,” in Proceedings of the 2nd International Workshop on Graph-Grammars and Their Application to Computer Science, Osnabrück (Germany), 1983, vol. 153, pp. 267–287.
LibreCat: /record/8255
DOI: dx.doi.org/10.1007/BFb0000113

G. Engels, R. Gall, M. Nagl, and W. Schäfer, “Software Specification Using Graph Grammars,” Computing, vol. 31, no. 4, pp. 317–346, 1983.
LibreCat: /record/7411
DOI: http://dx.doi.org/10.1007/BF02251236

G. Engels, U. Pletat, and H.-D. Ehrich, “An Operational Semantics for Specifications of Abstract Data Types with Error Handling,” Acta Informatica, vol. 9, no. 3, pp. 235–254, 1983.
LibreCat: /record/7412
DOI: http://dx.doi.org/10.1007/BF00265557

G. Engels and W. Schäfer, “Specification of a Programming Support Environment by Graph Grammars,” in Proceedings of the conference on Graphtheoretic Concepts in Computer Science (WG), München (Germany), 1982, pp. 47–62.
LibreCat: /record/7811

U. Pletat, G. Engels, and H.-D. Ehrich, “An Operational Approach to Conditional Algebraic Specifications,” in Proceedings of the 7eme Colloque sur les Arbres en Algebre et en Programmation, Lille (France), 1982, vol. 82, pp. 254–270.
LibreCat: /record/7812

G. Engels, U. Pletat, and H.-D. Ehrich, Handling Errors and Exceptions in the Algebraic Specifications of Data Types. University of Osnabrück, 1981.
LibreCat: /record/8184

U. Pletat, G. Engels, and H.-D. Ehrich, Operational Semantics of Algebraic Specifications with Conditional Equations. University of Dortmund, Department of Computer Science, 1981.
LibreCat: /record/8185