@inproceedings{ijcai1987p190,
  title     = {Matrix Proof Methods for Modal Logics},
  author    = {Wallen, Lincoln A.},
  booktitle = {Proceedings of the Tenth International Joint Conference on
               Artificial Intelligence, {IJCAI-87}},
  publisher = {International Joint Conferences on Artificial Intelligence},
  editor    = {John McDermott},
  pages     = {917--922},
  year      = {1987},
  note      = {Reasoning},
  url       = {https://ijcai.org/proceedings/1987/190},
}