Quasi-Valid Range Querying and Its Implications for Nearest Neighbor Problems.

Dan E. Willard Young C. Wee Quasi-Valid Range Querying and Its Implications for Nearest Neighbor Problems. 34-43 1988 Symposium on Computational Geometry http://doi.acm.org/10.1145/73393.73398 db/conf/compgeom/compgeom88.html#WillardW89