@inproceedings{UnifyingFramework,
  title = "A Unifying Framework for Tractable Constraints",
  author = "P.G.Jeavons and D.A.Cohen and M.Gyssens",
  year = "1995",
  booktitle = "Proceedings of the 1st International Conference on Principles and Practice of Constraint Programming (CP95)",
  pages = "276-291",
  series = "Lecture Notes in Computer Science",
  url = "ftp://ftp.cs.rhul.ac.uk/pub/constraints/unifying.ps",
  volume = "976",
  doi = "10.1007/3-540-60299-2_17",
}