Independently Published Secret Code Breaking Puzzles for Kids: Create and Crack 25 Codes and Cryptograms for Children aged 6 to 10. Great as a Gift for Junior Spies

Secret Code Breaking Puzzles for Kids: Create and Crack 25 Codes and Cryptograms for Children aged 6 to 10. Great as a Gift for Junior Spies

U.S.A. Secret Code Puzzles for Kids (Dover Kids Activity Books: U.S.A.)

The Junior Code Breaker Book: 50 intriguing code puzzles to crack: can you solve them all?