1. http://www.faa.gov/news/fact_sheets/news_story.cfm?newsid=8145
2. http://www.fleetmatics.com/
3. http://www.wirelessmatrix.com/
4. Montgomery , P. Y. Humphreys , E. T. Ledvina , B. M Receiver-Autonomous Spoofing Detection: Experimental Results of a Multi-Antenna Receiver Defense Against a Portable Civil GPS Spoofer Proceedings of the 2009 International Technical Meeting of The Institute of Navigation 2009 124 130
5. Ledvina , B. M. Bencze , J. W. Galusha , B. Miller , I. An In-Line Anti-Spoofing Device for Legacy Civil GPS Receivers Proceedings of the 2010 International Technical Meeting of The Institute of Navigation 2010 698 712