@inproceedings{ijcai1983p125,
  title     = {Prolog/Ex 1, An Inference Engine Which Explains Both Yes and No Answers},
  author    = {Walker, Adrian},
  booktitle = {Proceedings of the Eighth International Joint Conference on
               Artificial Intelligence, {IJCAI-83}},
  publisher = {International Joint Conferences on Artificial Intelligence},
  editor    = {Alan Bundy},
  pages     = {526--527},
  year      = {1983},
  note      = {Logic Programming},
  url       = {https://ijcai.org/proceedings/1983/125},
}