French, P. <br/><br/>
Cyphers 

 - 52p.; 20cm. 
 - Exploring mathematics .
<br/><br/><label>ISSN: </label>a 
<br/><br/><label>Subjects--Topical Terms: </label>--Ciphers--Signs and symbols
<br/><br/><label>Dewey Class. No.: </label>652 F8871c 1967