@article{OnTheAlgebraicStructure,
  title = "On The Algebraic Structure Of Combinatorial Problems",
  author = "P.G.Jeavons",
  year = "1998",
  journal = "Theoretical Computer Science",
  number = "200",
  pages = "185--204",
  url = "ftp://ftp.cs.rhul.ac.uk/pub/constraints/algebraic.ps",
}