A Study of Autonomous Mobile System in Outdoor Environment (Part 2: Sign Guided Autonomous Transportation System). - Jun-ichi Takiguchi; Kiyoshi Iwama; Hiroshi Sugie; Masanori Kato; Takayuki Kiyonaga; Takumi Hashizume; Fumihiro Inoue; Kyoji Yoshino; Yutaro Omote (ICRA, 1998)