References
- 1972 . Encyclopedia of Espionage London : New English Library . Cf. for instance the earlier Ronald Seth, ed
- 1997 . Spy Book: The Encyclopedia of Espionage New York : Random House of Canada; London: Greenhill books . Norman Polmar and Thomas B. Allen
- Telegram, German Naval Attaché in 3 Madrid to Admirality Staff, 3 May 1916. This and all other decrypts mentioned are in 5 N 82, Service Historique de L'Armée de Terre (SHA), Vincennes. German orignal of the telegram in Deutschland 179 sect./1, Politisches Archiv, Auswärtiges Amt, Berlin
- Telegram, German Military Attaché in 4 Madrid to General Staff, 7 August 1916 and 21 December 1916. In telegram, General Staff Berlin to German military attaché in Madrid, 1 August 1916, an agent was referred to by his full name. And the German naval attaché in Madrid frequently did so, too.
- Telegram, German Naval Attaché in 5 Madrid to Admirality Staff, 10 December 1916.
- “Spionage zugunsten Deutschlands hat 6 sie bestimmt getrieben, und ich bin der Meinung, dass sie von den Franzosen—leider—zu Recht erschossen wurde.” Generalmajor z.V. Gempp, Geheimer Nachrichtendienst und Spionageabwehr des Heeres (typescript) Vol .9 1941 Supplement to Annex 8, 3, Rw5/v.49, Bundesarchiv-Militärarchiv, Freiburg i.Br.