Links:

1. In the Shadow of Ultra: A Reappraisal of German Naval Communications Intelligence in 1914-1918

2. Very Special Intelligence: The Story of the Admiralty’s Operational Intelligence Centre 1939-1945

3.Room 40: British Naval Intelligence, 1914–1918

4. Germany's First Cryptanalysis on the Western Front: Decrypting British and French Naval Ciphers in World War I

5. Technology, Shipbuilding and Future Combat in Germany, 1880-1914.”

6. Sins of Omission and Commission: A Reassessment of the Role of Intelligence in the Battle of Jutland

7. Ludwig Föppl: A Bavarian Cryptanalyst on the Western Front

8. The Ultra Secret