TY  - BOOK
AU  - D'Agapeyeff,Alexander
TI  - Codes and ciphers
U1  - 652.8 
PY  - 1952///
CY  - London
PB  - G. Cumberlege, Oxford university press
KW  - Ciphers
KW  - Cryptography
N1  - Bibliography: p. 145-146. and index
ER  -