@inproceedings{ijcai2009p98,
  title     = {Variety Reasoning for Multiset Constraint Propagation},
  author    = {Law, Yat Chiu and Lee, Jimmy Ho-Man and Woo, May H. C.},
  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     = {552--557},
  year      = {2009},
  url       = {https://ijcai.org/proceedings/2009/98},
}