Victor M. Markowitz, Yoav Raz. A Modified Relational Algebra and its Use in an Entity-Relationship Environment. In Carl G. Davis, Sushil Jajodia, Peter A. Ng, Raymond T. Yeh, editors, Proceedings of the 3rd Int. Conf. on Entity-Relationship Approach (ER 83). pages 315-328, North-Holland, 1983. [doi]
Abstract is missing.