1. Agrawal, R., "Alpha: An Extension of Relational Algebra to Express a Class of Recursive Queries," Proc. IEEE 3rd Int. Conf. Data Engineering, Los Angeles, Feb. 1987, pp. 580–590.
2. Agrawal, R., Dar, S., Jagadish, H.V., "Transitive Closure Algorithms Revisited: The Case of Path Computations," Submitted for publication.
3. Agrawal, R., Jagadish, H.V., "Direct Algorithms for Computing the Transitive Closure of Database Relations," Proc. of the 13th VLDB Conf., Brighton 1987, pp. 255–266.
4. Biskup, J., Raesch, U., Stiefeling, H., "An Extended Relational Query Language for Knowledgebase Support," Hildesheimer Informatik-Berichte, 1987, Hochschule Hildesheim.
5. Biskup, J., Raesch, U., Stiefeling, H., "Report on Structure and Complexity of Several Augmented Relational Algebras," ESPRIT Project 311: ADKMS, Deliverable D12.