@inproceedings{conf/vldb/GottlobZ88,
  title = "Closed World Databases Opened Through Null Values",
  author = "Georg Gottlob and Roberto Zicari",
  year = "1988",
  booktitle = "{Fourteenth International Conference on Very Large Data Bases, August 29 - September 1, 1988, Los Angeles, California, USA,
Proceedings}",
  editor = "Fran\c{c}ois Bancilhon and David J. DeWitt",
  isbn = "0-934613-75-3",
  pages = "50-61",
  publisher = "Morgan Kaufmann",
  url = "http://www.informatik.uni-trier.de/~ley/db/conf/vldb/GottlobZ88.html",
}