TY  - BOOK
AU  - Pratt,Fletcher
TI  - Secret and urgent, the story of codes and ciphers
PY  - 1942///]
CY  - Garden city, N.Y.
PB  - Blue ribbon Books
KW  - Cryptography
KW  - Ciphers
KW  - Cryptographie
N1  - Includes index
ER  -