@article{ConstraintsAndUniversalAlgebra,
  title = "Constraints and Universal Algebra",
  author = "P.G.Jeavons and D.A.Cohen and J.K.Pearson",
  year = "1998",
  journal = "Annals of Mathematics and Artificial Intelligence",
  number = "24",
  pages = "51--67",
  url = "ftp://ftp.cs.rhul.ac.uk/pub/constraints/con_and_universal.ps",
}