M. Samer, St. Szeider:
"Tractable Cases of the Extended Global Cardinality Constraint";
Constraints, 16 (2011), 1; 1 - 24.
http://dx.doi.org/10.1007/s10601-009-9079-yElectronic version of the publication:
http://publik.tuwien.ac.at/files/PubDat_200949.pdf