Roddy, D., Au. <br/><br/>
Electronic communications 

 - 3rd,4th 
 - New Delhi  Prentice-Hall of India  1994 
 - 788p. 
<br/><br/><label>ISBN: </label>8120303962 
<br/><br/><label>Dewey Class. No.: </label>621.38  / R69E