[Regin 1994] R ´ egin, J.-C. 1994. A filtering algorithm for ´
constraints of difference in CSPs. In *12th Nat. Conf. on AI*,
362–367.

[Stergiou & Walsh 1999] Stergiou, K., and Walsh, T. 1999.

The difference all-difference makes. In *Proc. of 16th IJCAI*,
414–419.