Yin Yang Stavros Papadopoulos Dimitris Papadias George Kollios Spatial Outsourcing for Location-based Services. 1082-1091 2008 ICDE http://dx.doi.org/10.1109/ICDE.2008.4497517 conf/icde/2008 db/conf/icde/icde2008.html#YangPPK08