1. SEQUEL 2: A unified approach to data definition, manipulation, and control;Chamberlin;IBM Journal of Research and Development,1976
2. CODASYL Data base Task Group Report,1971
3. An Introduction to Database Systems;Date,1977
4. Data organization;Durding;Human Factors,1977
5. Use of an IQF-like query language by non-programmers;Gould;IBM Research Report RC 5279,1975