Frank Drewes, Annegret Habel, Hans-Jörg Kreowski: Hyperedge Replacement Graph Grammars. In G. Rozenberg, editor, Handbook of Graph Grammars and Computing by Graph Transformation. Vol. 1: Foundations, chapter 2, pages 95-162. World Scientific, 1997.
Frank Drewes, Hans-Jörg Kreowski, Denis Lapoire: Criteria to Disprove Context-Freeness of Collage Languages. In B.S. Chlebus, L. Czaja, editors, Proc. Fundamentals of Computation Theory XI, volume 1279 of Lecture Notes in Computer Science, pages 169-178. 1997.
Hans-Jörg Kreowski, Sabine Kuske, Andy Schürr: Nested graph transformation units. International Journal on Software Engineering and Knowledge Engineering 7:479-502, 1997.
Hartmut Ehrig, Hans-Jörg Kreowski, Fernando Orejas: Correctness of Horizontal and Vertical Composition for Implementation Concepts Based on Constructors and Abstractors. Revista Matematica 10:365-387, 1997.
