Donnie H. Kim Jeffrey Hightower Ramesh Govindan Deborah Estrin Discovering semantically meaningful places from pervasive RF-beacons. 21-30 2009 UbiComp http://doi.acm.org/10.1145/1620545.1620549 conf/huc/2009 db/conf/huc/ubicomp2009.html#KimHGE09