Thalheim89'

BibTeX

@article{DBLP:journals/eik/Thalheim89,
  author    = {Bernhard Thalheim},
  title     = {On Semantic Issues Connected with Keys in Relational Databases
               Permitting Null Values},
  journal   = {Elektronische Informationsverarbeitung und Kybernetik},
  volume    = {25},
  number    = {1/2},
  year      = {1989},
  pages     = {11-20},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}