@article{Codd70,
  author	= {Codd, E. F.},
  month		= jun,
  year		= {1970},
  title		= {A Relational Model of Data for Large Shared Data Banks},
  journal	= {Comm. ACM},
  volume	= {13},
  number	= {6},
  pages		= {pages 377--387}
}