Roddy, Dennis <br/><br/>
Electronic communications 
/ Dennis Roddy, John Coolen, ... 
. - 3rd ed. 
. - Virginia  : Reston, 1984
. - XII-788 p.  : ill.  ; 25 cm. 
<br/><br/>Index 
<br/><br/><label>ISBN: </label>0835915980 
<br/><br/><label>Source: </label> Don 
<br/><br/><label>Universal Decimal Class. No.: </label>621.39