Benry, Beker. Piper, Fred. <br/><br/>
Circute Systems.   The Protection of Communications 

 - Londen  Northwood  1982 
 - 24X16 427 
<br/><br/><label>ISBN: </label>719826611X  719825717 
<br/><br/><label>Dewey Class. No.: </label>621.3852 B424