Enrico Giunchiglia Joohyung Lee Vladimir Lifschitz Norman McCain Hudson Turner Nonmonotonic causal theories. 49-104 2004 153 Artif. Intell. 1-2 http://dx.doi.org/10.1016/j.artint.2002.12.001 db/journals/ai/ai153.html#GiunchigliaLLMT04