1. P. Buneman, R. Nikhil: The Functional Data Model and its Use for Interaction with Databases. In: [BMS84] (359 – 380)
2. R.A. Elmasri, J. Weeldreyer, A. Hevner: The Category Concept: An Extension to the Entity-Relationship Model. Data and Knowledge Engineering 1985, Vol. 1 (75 – 116)
3. J.A. Makowski, V.M. Markowitz, N. Rotics: Entity-Relationship Consistency for Relational Schemes.In G. Ausiello, P. Atzeni (eds.): Proc. International Conference on Database Theory ICDT 1986, Springer LNCS 243 (306 – 322)
4. T.J. Teorey, D. Yang, J.P. FRY: A Logical Design Methodology for Relational Databases Using the Extended Entity-Relationship Model. ACM Computing Surveys 1986, 18(2) (197 – 222)
5. U. Hohenstein, M. Gogolla: A Calculus for an Extended Entity-Relationship Model Incorporating Arbitrary Data Operations and Aggregate Functions. In: [ERA88] (129 —148)