@article{SamerSzeider11,
 author = {Marko Samer and
Stefan Szeider},
 doi = {10.1007/s10601-009-9079-y},
 journal = {Constraints},
 number = {1},
 pages = {1-24},
 title = {Tractable cases of the extended global cardinality constraint},
 volume = {16},
 year = {2011}
}