TY  - BOOK
AU  - Zim,Herbert S.
TI  - Codes & secret writing
AV  - Z104 .Z5 1965
U1  - 652.8 
PY  - 1948///, 1975 printing
CY  - New York
PB  - Scholastic Book Services
KW  - Cryptography
UR  - http://www.archive.org/details/codessecretwriti00zimh
UR  - http://www.openlibrary.org/books/OL24203635M
ER  -