Books & Magazines
Operation Fortitude - Joshua Levine - 2011
Chapter 7 contains information on Josef. Well-researched - author cites information from the KV files at the PRO.
Tales from the Tower - Daniel Diehl & Mark P Donnelly - 2005
Chapter 15 contains information on Josef. Fictionalized history - several inaccuracies and errors.
Camp 020 - MI5 and the Nazi spies - Oliver Hoare - 2000
Several references to Josef. Based on Camp 020 files.
Shot in the Tower - Leonard Sellers - 1997
Primarily about WWI German spies executed in the Tower. An Appendix on Josef
MI5 - British Security Service Operations, 1909-1945 - Nigel West - 1982
Several references to Josef.
Double-Cross System - John C. Masterman - 1972
Short reference to Josef.
After the Battle Magazine - Volume 11 - German Spies in Britain - 1976
40 years old and superseded by more accurate information, but still a foundational article on Josef.