[4] Abschlussbericht vom 29. August 2001: ,Vulnerability assessment of the transportation infrastructure relying on the global positioning system", zusammengestellt von John A. Volpe, National Transportation Systems Center.
[4] Eindrapport, van 29 augustus 2001 : "Vulnerability assessment of the transportation infrastructure relying on the global positioning system", opgesteld door John A. Volpe National Transportation Systems Center.