@inproceedings{ijcai1981p157,
  title     = {Extending a Knowledge-Based System to Deal with Ad Hoc Constraints},
  author    = {McDermott, John P. and Steele, Barbara},
  booktitle = {Proceedings of the Seventh International Joint Conference on
               Artificial Intelligence, {IJCAI-81}},
  publisher = {International Joint Conferences on Artificial Intelligence},
  editor    = {Roger C. Schank},
  pages     = {824--827},
  year      = {1981},
  month     = {8},
  note      = {Expert Systems},
  url       = {https://ijcai.org/proceedings/1981/157},
}