TY  - BOOK
AU  - Pratt,Fletcher
TI  - Secret and urgent: the story of codes and ciphers
U1  - 652.809 
PY  - 1939///
CY  - London
PB  - Robert Hale
KW  - Cryptography
KW  - Sings and symbols
KW  - Symbolism
N1  - Includes index
ER  -