Ebert, J., &; Engels, G. (1994). Observable or Invocable Behaviour - You Have to Choose. Vakgroep Informatica, Rijksuniversiteit Leiden.

Andries, M., &; Engels, G. (1994). Syntax and Semantics of Hybrid Database Languages. In Proceedings of the International Workshop on Graph Transformations in Computer Science (1993), Dagstuhl (Germany) (Vol. 776, pp. 19–36). Berlin/Heidelberg: Springer.http://dx.doi.org/10.1007/3-540-57787-4_2 

Engels, G., &; Groenewegen, L. (1994). Specification of coordinated behaviour by SOCCA. In Proceedings of the Third European Workshop on Software Process Technology (EWSPT 1994), Villard de Lans (France) (pp. 128–151). Berlin/Heidelberg: Springer.http://dx.doi.org/10.1007/3-540-57739-4_19 

Engels, G., &; Löhr, P. (1994). Visual Specification of Complex Database Actions. In Proceedings of the 2nd International East/West Database Workshop, Klagenfurt (Germany) (pp. 303–314). Berlin/Heidelberg: Springer.

Löhr-Richter, P., &; Engels, G. (1994). Visuelles Spezifizieren von komplexen Aktionen auf Datenbankstrukturen. GI-Datenbank Rundbrief, 13, 33–35.

Ebert, J., &; Engels, G. (1994). Design Representation. In Encyclopedia of Software Engineering (pp. 382–394). John Wiley &; Sons, Inc.

Engels, G., &; Groenewegen, L. (1994). SOCCA: Specifications of Coordinated and Cooperative Activities. In Software Process Modelling and Technology (pp. 71–102). Taunton: Research Studies Press.

Engels, G., &; Verrijn-Stuart, A. A. (1993). Integrationsaspekte bei verteilter Software-Entwicklung. In Fortschritt-Berichte VDI (pp. 45–53). VDI Verlag.

Andries, M., &; Engels, G. (1993). A Hybrid Query Language for the Extended Entity Relationship Model. Vakgroep Informatica, Rijksuniversiteit Leiden.

Ehrig, H., &; Engels, G. (1993). Towards a Module Concept for Graph Transformation Systems. Vakgroep Informatica, Rijksuniversiteit Leiden.

Engels, G., &; Rozenberg, G. (1993). Abstracts COMPUGRAPH II Workshop. Vakgroep Informatica, Rijksuniversiteit Leiden.

Engels, G., &; Groenewegen, L. (1993). Modular, Visual Specifications of Software Processes. In Proceedings of the Workshop on Software Process (ISPW 1993), Wadern (Germany) (pp. 66–68). Washington, DC, USA: IEEE Computer Society.

Koopman, P., Groenewegen, L., &; Engels, G. (1992). Functional Description of Parallel Processes. In Proceedings of the conference SION Computing Science in the Netherlands (CSN ’92), The Netherlands (pp. 156–167).

Engels, G. (1992). Visual Specifications of Conceptual Database Schemata (Abstract). Leiden University.

Engels, G., &; Löhr-Richter, P. (1992). CADDY: A Highly Integrated Environment to Support Conceptual Database Design. In Proceedings of the Fifth International Workshop on Computer-Aided Software Engineering (CASE 1992), Montreal (Canada) (pp. 19–22). Washington, DC, USA: IEEE Computer Society.

Engels, G., &; Groenewegen, L. (1992). Specification of Coordinated Behaviour in the Software Development Process. In Proceedings of the Second European Workshop on Software Process Technology (EWSPT 92), Trondheim, Norway (Vol. 635, pp. 58–60). Berlin/Heidelberg: Springer.http://dx.doi.org/10.1007/BFb0017495 

Hohenstein, U., &; Engels, G. (1992). SQL/EER - Syntax and Semantics of an Entity-Relationship-Based Query Language. Information Systems, 17(3), 209–242.http://dx.doi.org/10.1016/0306-4379(92)90014-E 

Engels, G., Lewerentz, C., Nagl, M., Schäfer, W., &; Schürr, A. (1992). Building Integrated Software Development Environments, Part I: Tool Specification. ACM Transactions on Software Engineering and Methodology (TOSEM), 1(2), 135–167.

Engels, G., Gogolla, M., Hohenstein, U., Hülsmann, K., Löhr-Richter, P., Saake, G., &; Ehrich, H.-D. (1992). Conceptual Modelling of Database Applications Using an Extended ER Model. Data &; Knowledge Engineering, 9(2), 157–204.http://dx.doi.org/10.1016/0169-023X(92)90008-Y 

Löhr-Richter, P., &; Engels, G. (1991). Incremental Design of Conceptual Database Schemata with CADDY. Leiden University, P.O. Box 9500, 2300 RA Leiden, The Netherlands: Leiden University.