The Relational and Network Approaches: Comparison of the Application Programming Interfaces.

http://doi.acm.org/10.1145/800297.811532 db/conf/sigmod/DateC74.html C. J. Date E. F. Codd The Relational and Network Approaches: Comparison of the Application Programming Interfaces. 83-113 SIGFIDET74-2/P083.pdf 1974 conf/sigmod/74 SIGMOD Workshop, Vol. 2 db/conf/sigmod/sigmod74-2.html#DateC74