Kahn, D. (1967). The codebreakers: The story of secret writing (First edition.). The Macmillan Company.

Kahn, David. The Codebreakers: The Story of Secret Writing. First edition. New York: The Macmillan Company, 1967.

Kahn, David. The Codebreakers: The Story of Secret Writing. First edition. The Macmillan Company, 1967.