O'Brien, Eileen.

The Usborne book of secret codes / Secret codes Eileen O'Brien and Diana Riddell ; illutrated by Mark Watkinson ; photographs by Howard Allman. - New York : London, Eng., Scholastic ; Usborne, 1998, c1997. - 32 p. : col. ill. ; 25 cm.

ISBN: 0590631527

Subjects--Topical Terms:
Cryptography.

Dewey Class. No.: 652.8