* Central Intelligence Agency: "The Rote Kapelle" Washington 1984* Harry Hinsley: "British Intelligence in the Second World War" London 1979-1988* Phillip Knightley: "The Second Oldest Profession" W.W. Noron & Co, 1986 ISBN 0-393-2386-9* Read, Anthony, and David Fisher.
*Central Intelligence Agency: "The Rote Kapelle" Washington 1984*Hinsley, Francis Harry: "British Intelligence in the Second World War" London 1979-1988*Knightley, Phillip: "The Second Oldest Profession" W.W. Noron & Co, 1986 ISBN 0-393-2386-9* Read, Anthony, and David Fisher.