Anmol Sheth Srinivasan Seshan David Wetherall Geo-fencing: Confining Wi-Fi Coverage to Physical Boundaries. 274-290 2009 Pervasive http://dx.doi.org/10.1007/978-3-642-01516-8_19 conf/pervasive/2009 db/conf/pervasive/pervasive2009.html#ShethSW09