1. A. Aho, R. Sethi, and J. Ullman. Compilers: principles, techniques, and tools. Addison-Wesley, Reading, Massachusetts, 1986.
2. E. Baralis. An Algebraic Approach to the Analysis and Optimization of Active Database Rules. PhD thesis, Politecnico di Torino, Torino, Italy, Feb. 1994.
3. E. Baralis, S. Ceri, G. Monteleone, and S. Paraboschi. An intelligent database system application: The design of EMS. In Proc. of the First Int. Conf. on Applications of Databases, LNCS 851, Vadstena, Sweden, June 1994. Springer-Verlag.
4. S. Ceri and G. Gottlob. Translating SQL into relational algebra: Optimization, semantics, and equivalence of SQL queries. IEEE Trans. Softw. Eng., 11(4):324–345, Apr. 1985.
5. S. Ceri and R. Manthey. Consolidated specification of Chimera, the conceptual interface of Idea. Technical Report IDEA.DD.2P.004, Politecnico di Milano, Milan, Italy, June 1993.