@InProceedings{hill-fernandez99neg:agp,
  Author = "A. Fern\'{a}ndez and P. M. Hill",
  Title = "Negative Constraints",
  Pages = "105--120",
  Crossref = "AGP99",
}

@Proceedings{AGP99,
  Title = "Proceedings of the
           ``APPIA-GULP-PRODE'99
           Joint Conference on Declarative Programming''",
  BookTitle = "Proceedings of the
               ``APPIA-GULP-PRODE'99
               Joint Conference on Declarative Programming''",
  Editor = "M. C. Meo and M. Vilares Ferro",
  Address = "L'Aquila, Italy",
  Year = 1999,
}