@inproceedings{AlgebraicCharacterisation,
  title = "An algebraic characterisation of complexity for valued constraints",
  author = "David Cohen and Martin Cooper and Peter Jeavons",
  year = "2006",
  booktitle = "Proceedings of the 12th International Conference on Principles and Practice of Contraint Programming (CP'06)",
  pages = "107-121",
  series = "Lecture Notes in Computer Science",
  url = "http://www.comlab.ox.ac.uk/activities/constraints/publications/CP06expressibility.pdf",
  volume = "4204",
  doi = "10.1007/11889205_10",
}