Warning - the bibtex entry below may be invalid: 
Missing 'booktitle' field 
@inproceedings{ComplexityOfSoft,
  author = "David Cohen and Martin Cooper and Peter Jeavons and Andrei Krokhin",
  doi = "10.1016/j.artint.2006.04.002",
  journal = "Artificial Intelligence",
  pages = "983-1016",
  title = "The complexity of soft constraint satisfaction",
  url = "http://web.comlab.ox.ac.uk/oucl/research/areas/constraints/publications/AIJ-3418.pdf",
  volume = "170",
  year = "2006",
}