Welsh, Dominic <br/><br/>
Codes and cryptography / 
Dominic Welsh 
 - Oxford :  Clarendon Press,  1988 
 - 257 p. :  ill. ;  23 cm. 
<br/><br/><label>ISBN: </label>0198532873 
<br/><br/><label>LCCN: </label>87-31354 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Cryptography<br/>Ciphers