@Inproceedings{BagnaraHZ04,
  Author = "R. Bagnara and P. M. Hill and E. Zaffanella",
  Title =  "Widening Operators for Powerset Domains",
  Booktitle = Proceedings of the 5th International Conference on
              Verification, Model Checking and Abstract Interpretation",
  Editor = "G. Levi and B. Steffen",
  Pages = "135-148",
  Publisher = "Springer",
  Series = "LNCS",
  Volume = "2937",
  Year = 2004,
  Month = "January",
}