Yoshiharu Ishikawa Yuichi Tsukamoto Hiroyuki Kitagawa Extracting Mobility Statistics from Indexed Spatio-Temporal Datasets. 9-16 2004 conf/stdbm/2004 STDBM http://db.cs.ualberta.ca/stdbm04/Proceedings/02.pdf db/conf/stdbm/stdbm2004.html#IshikawaTK04