Donald D. Chamberlin Morton M. Astrahan Kapali P. Eswaran Patricia P. Griffiths Raymond A. Lorie James W. Mehl Phyllis Reisner Bradford W. Wade SEQUEL 2: A Unified Approach to Data Definition, Manipulation, and Control. 560-575 1976 20 IBM Journal of Research and Development 6 db/journals/ibmrd/ibmrd20.html#ChamberlinAEGLMRW76 db/journals/ibmrd/ChamberlinAEGLMRW76.html ibmrd/20/P560.pdf