Codd, E.F. A Relational Model of Data for Large Shared Data Banks. Communications of the ACM, Vol. 13, No. 6, June 1970, ss. 377–387, tillgänglig härArkiverad 12 juni 2007 hämtat från the Wayback Machine.
portal.acm.org
Donald D. Chamberlin and Raymond F. Boyce, 1974. "SEQUEL: A structured English query language", International Conference on Management of Data, Proceedings of the 1974 ACM SIGFIDET (now SIGMOD) workshop on Data description, access and control, Ann Arbor, Michigan, pp. 249–264
Codd, E.F. A Relational Model of Data for Large Shared Data Banks. Communications of the ACM, Vol. 13, No. 6, June 1970, ss. 377–387, tillgänglig härArkiverad 12 juni 2007 hämtat från the Wayback Machine.