@inproceedings{ijcai2009p102,
  title     = {Open Contractible Global Constraints},
  author    = {Maher, Michael J.},
  booktitle = {Proceedings of the Twenty-First International Joint Conference on
               Artificial Intelligence, {IJCAI-09}},
  publisher = {International Joint Conferences on Artificial Intelligence},
  editor    = {Hiroaki Kitano},
  pages     = {578--582},
  year      = {2009},
  url       = {https://ijcai.org/proceedings/2009/102},
}