1. Cooperative answering: a methodology to provide intelligent access to databases;Cuppens,1988
2. Amalgamating language and metalalanguage in Logic Programming;Bowen,1980
3. The limitations of Logic;Kowalski,1986
4. Relational completeness of data base sublanguages;Codd,1972
5. Syntactical characterization of a subset of domain independent formulas;Demolombe,1982