Tim Kindberg Chris Bevan Eamonn O'Neill James Mitchell Jim Grimmett Dawn Woodgate Authenticating ubiquitous services: a study of wireless hotspot access. 115-124 2009 UbiComp http://doi.acm.org/10.1145/1620545.1620565 conf/huc/2009 db/conf/huc/ubicomp2009.html#KindbergBOMGW09