@inproceedings{ijcai1979p94,
  title     = {How Not to Say "NIL": Improving Answers to Failing Queries in Data Base Systems},
  author    = {Janas, Jürgen M.},
  booktitle = {Proceedings of the Sixth International Joint Conference on
               Artificial Intelligence, {IJCAI-79}},
  publisher = {International Joint Conferences on Artificial Intelligence},
  editor    = {Bruce G. Buchanan},
  year      = {1979},
  month     = {8},
  url       = {https://ijcai.org/proceedings/1979/94},
}