@inproceedings{HowToDetermine,
  title = "How to determine the expressive power of constraints",
  author = "P.G.Jeavons and D.A.Cohen and M.Gyssens",
  year = "1999",
  booktitle = "Constraints",
  number = "4",
  pages = "113--131",
  url = "ftp://ftp.cs.rhul.ac.uk/pub/constraints/how_to_determine.ps",
}