@inproceedings{ijcai1969p54,
  title     = {A Formal Description for Two-Dimensional Patterns},
  author    = {Jr., Charles T. Zahn},
  booktitle = {Proceedings of the First International Joint Conference on
               Artificial Intelligence, {IJCAI-69}},
  publisher = {International Joint Conferences on Artificial Intelligence},
  editor    = {Donald E. Walker and David C. Cooper},
  pages     = {621--628},
  year      = {1969},
  month     = {5},
  note      = {Linguistic and Contextual Methods in Pattern Recognition},
  url       = {https://ijcai.org/proceedings/1969/54},
}