Hiroyuki Toda Norihito Yasuda Yumiko Matsuura Ryoji Kataoka Incorporating place name extents into geo-ir ranking. 1489-1490 2008 CIKM http://doi.acm.org/10.1145/1458082.1458349 conf/cikm/2008 db/conf/cikm/cikm2008.html#TodaYMK08