@inproceedings{ijcai1979p144,
  title     = {Problem Solving of Elementary Algebra by Hierarchical Abstraction},
  author    = {Nishida, Fujio and Fujita, Yoneharu and Kusaka, Hiroji},
  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/1979/144},
}