@inproceedings{cjz07:cp,
  title = "The Expressive Power of Valued Constraints: Hierarchies and Collapses",
  author = "David A. Cohen and Peter G. Jeavons and Stanislav \v{Z}ivn\'y",
  year = "2007",
  booktitle = "{P}roceedings of the 13th {I}nternational {C}onference on {P}rinciples and {P}ractice of {C}onstraint {P}rogramming ({C}{P}'07)",
  pages = "798--805",
  publisher = "Springer",
  series = "Lecture Notes in Computer Science",
  url = "http://zivny.cz/publications/cjz07cp-preprint.pdf",
  volume = "4741",
  doi = "10.1007/978-3-540-74970-7_57",
}