Krokhin, A., Bulatov, A., & Jeavons, P. (2005). The complexity of constraint satisfaction: an algebraic approach. In V. B. Kudryavtsev, & I. G. Rosenberg (Eds.), Structural theory of automata, semigroups, and universal algebra (181-213). Springer Netherlands. https://doi.org/10.1007/1-4020-3817-8_8