@inproceedings{Zivny07:cp,
  author = "David A. Cohen and Peter G. Jeavons and Stanislav \v{Z}ivn{\'y}",
  booktitle = "Proceedings of the 13th International Conference on Principles and Practice of Constraint Programming (CP'07)",
  doi = "http://www.springerlink.com/content/c166730ur4301301/",
  month = "September",
  note = "(full version submitted to a journal)",
  pages = "798--805",
  series = "LNCS",
  title = "Thee expressive power of valued constraints: hierarchies and collapses",
  url = "http://www.springerlink.com/content/c166730ur4301301/",
  volume = "4741",
  year = "2007",
}