Oliver Kullmann Upper and Lower Bounds on the Complexity of Generalised Resolution and Generalised Constraint Satisfaction Problems. 303-352 2004 40 Ann. Math. Artif. Intell. 3-4 http://dx.doi.org/10.1023/B:AMAI.0000012871.08577.0b db/journals/amai/amai40.html#Kullmann04