Bamford, James; The Shadow Factory: The Ultra-Secret NSA from 9/11 to the Eavesdropping on America, Doubleday, ISBN 0385521324; 2008
Hager, Nicky; Secret Power, New Zealand's Role in the International Spy Network; Craig Potton Publishing, Nelson, NZ; ISBN 0-908802-35-8; 1996
Keefe, Patrick Radden Chatter: dispatches from the secret world of global eavesdropping; Random House Publishing, New York, NY; ISBN 1-4000-6034-6; 2005