Francesco Buccafurri Nicola Leone Pasquale Rullo Stable Models and Their Computation for Logic Programming with Inheritance and True Negation. 5-43 1996 27 J. Log. Program. 1 db/journals/jlp/jlp27.html#BuccafurriLR96 http://dx.doi.org/10.1016/0743-1066(95)00076-3