Andrei A. Bulatov Andrei A. Krokhin Benoit Larose Dualities for Constraint Satisfaction Problems. 93-124 2008 Complexity of Constraints http://dx.doi.org/10.1007/978-3-540-92800-3_5 conf/dagstuhl/2008coc db/conf/dagstuhl/coc2008.html#BulatovKL08