1. Geolocation and assisted GPS
2. eMarketer. "One Billion Mobile Users by End of Q2," http://www.nua.ie/surveys/index.cgi?f=VS&art_id=905357779&rel=true, 28 April 2002.
3. Frost and Sullivan. "M-Commerce Transactions to Hit USD25 Billion," http://www.nua.ie/surveys/index.cgi?f=VS&art_id=905357769&rel=true, 29 April 2002.
4. Frost and Sullivan. North American Location-Based Service Markets, http://www.frost.com/, 25 March 2003.
5. Greening, D. "Location Privacy," http://www.openmobilealliance.org/lif/, 27 May 2003.