Ken C. K. Lee Josh Schiffman Baihua Zheng Wang-Chien Lee Valid scope computation for location-dependent spatial query in mobile broadcast environments. 1231-1240 2008 CIKM http://doi.acm.org/10.1145/1458082.1458245 conf/cikm/2008 db/conf/cikm/cikm2008.html#LeeSZL08