Specifying Queries as Relational Expressions: The SQUARE Data Sublanguage.

@article{DBLP:journals/cacm/BoyceCKH75,
  author    = {Raymond F. Boyce and
               Donald D. Chamberlin and
               W. Frank King III and
               Michael Hammer},
  title     = {Specifying Queries as Relational Expressions: The SQUARE Data
               Sublanguage},
  journal   = {Commun. ACM},
  volume    = {18},
  number    = {11},
  year      = {1975},
  pages     = {621-628},
  ee        = {db/journals/cacm/BoyceCKH75.html},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}

Abstract

Copyright © 1975 by the ACM, Inc., used by permission. Permission to make digital or hard copies is granted provided that copies are not made or distributed for profit or direct commercial advantage, and that copies show this notice on the first page or initial screen of a display along with the full citation.

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