"Machine Cryptography and Modern Cryptanalysis", Artech House, 1985. ISBN 0-89006-161-0. Karl de Leeuw, "The Dutch invention ofthe rotor machine, 1915 - 1923
法務部調查局: 19. [2012-02-03] (中文(繁體)). [永久失效連結] Helen Fouché Gaines, Cryptanalysis: a Study of Ciphers and Their Solutions (1989), page 6] Biliteral can mean: