Yohei Iwasaki Nobuo Kawaguchi Yasuyoshi Inagaki Azim: Direction-Based Service System for Both Indoors and Outdoors. 1034-1044 2005 88-B IEICE Transactions 3 http://dx.doi.org/10.1093/ietcom/e88-b.3.1034 db/journals/ieicet/ieicet88b.html#IwasakiKI05