Files W.F.F. Archive Publications War Department, Office of the Chief Signal Officer, Military Cryptanalysis, Part III, 1939 (with Minor Revisions); Solution of Progressive-Alphabet Cipher with Unknown Mixed Primary Alphabets; Solution of Progressive-Alphabet Cipher with Standard Plaintext Alphabet and Unknown Mixed Cipher Alphabet; Solution of Plain Text Auto Key Problem Using Unknown Identical Primaries by Paul H. Burdick, September 1941
Military Cryptanalysis, Part III: Simpler Varieties of Aperiodic Substitution Systems
Solution of Plain Text Auto Key Problem Using Unknown Identical Primaries
Solution of Progressive-Alphabet Cipher with Standard Plaintext Alphabet and Unknown Mixed Cipher Alphabet; Describes Techniques Used In Describing the Solution Process