Claudette Cayrol Marie-Christine Lagasquie-Schiex Thomas Schiex Nonmonotonic Reasoning: From Complexity to Algorithms. 207-236 1998 22 Ann. Math. Artif. Intell. 3-4 db/journals/amai/amai22.html#CayrolLS98 http://dx.doi.org/10.1023/A:1018939502485