Jan Chomicki Dina Q. Goldin Gabriel M. Kuper David Toman Variable Independence in Constraint Databases. 1422-1436 2003 15 IEEE Trans. Knowl. Data Eng. 6 http://doi.ieeecomputersociety.org/10.1109/TKDE.2003.1245282 db/journals/tkde/tkde15.html#ChomickiGKT03