Steven Strachan Roderick Murray-Smith Nonvisual, Distal Tracking of Mobile Remote Agents in Geosocial Interaction. 88-102 2009 LoCA http://dx.doi.org/10.1007/978-3-642-01721-6_6 conf/loca/2009 db/conf/loca/loca2009.html#StrachanM09