Chih-Chieh Hung Chih-Wen Chang Wen-Chih Peng Mining trajectory profiles for discovering user communities. 1-8 2009 GIS-LBSN http://doi.acm.org/10.1145/1629890.1629892 conf/gis/2009lbsn db/conf/gis/lbsn2009.html#HungCP09