Bibliography
- Grzegorz Łukomski and Rafał E. Stolarski, Nie tylko Enigma... Mjr Rudolf Gundlach (1892-1957) i jego wynalazek (Not Only Enigma... Major Rudolf Gundlach (1892-1957) and His Invention), Warsaw-London, 1999.
Read more about this topic: Rudolf Gundlach