Keeley 2008 States "Professor Denis Smyth, of the University of Toronto, an expert on Second World War intelligence operations, said that the British codebreaker Alfred Dilwyn Knox cracked the code of Franco's machine in 1937, but 'this information was not passed on to the Republicans.'" Keeley, Graham (24 October 2008), "Nazi Enigma machines helped General Franco in Spanish Civil War", The Times, p. 27, retrieved 15 May 2020
Bt, Sir William Arbuthnot. "Table E part 2". www.kittybrewster.com. Archived from the original on 15 June 2006.{{cite web}}: CS1 maint: unfit URL (link)
