1. Dependency structures of database relationships;Armstrong,1974
2. The theory of joins in relational data bases;Aho,1977
3. Equivalences among relational expressions;Aho;SIAM J. Comput.,1978
4. Universality of data retrieval languages;Aho,1979
5. On the completeness of query languages for relational data bases;Bancilhon,1978