@Techreport{BagnaraHMZ05TR,
  Author = "R. Bagnara and P. M. Hill and E. Mazzi and E. Zaffanella",
  Title = "Widening Operators for Weakly-Relational Numeric Abstractions",
  Number = 399,
  Type = "Quaderno",
  Institution = "Dipartimento di Matematica, Universit\`a di Parma, Italy",
  Year = 2005,
  Note = "Available at \url{http://www.cs.unipr.it/Publications/}"
}