Logic Programming and Nonmonotonic Reasoning 5th International Conference, LPNMR '99, El Paso, Texas, USA, December 2-4, 1999 Proceedings - Gelfond, Michael; Gelfond, Michael; Leone, Nicole; Leone, Nicole; Pfeifer, Gerald; Pfeifer, Gerald (Springer Berlin Heidelberg : Imprint: Springer, 1999)