Masahiro Bessho Shinsuke Kobayashi Noboru Koshizuka Ken Sakamura A space-identifying ubiquitous infrastructure and its application for tour-guiding service. 1616-1621 2008 SAC http://doi.acm.org/10.1145/1363686.1364069 conf/sac/2008 db/conf/sac/sac2008.html#BesshoKKS08