Welsh, Dominic <br/><br/>
Codes and cryptography / 
Dominic Welsh 
 - Oxford,  Oxford University Press,  1998. 
 - ix, 257 p. ;  24 cm. 
<br/><br/><label>ISBN: </label>9780198532873 (pbk.) 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Ciphers.<br/>Cryptography.
<br/><br/><label>Dewey Class. No.: </label>652.8 WEL