Held, Gilbert, <br/><br/>
Understanding data communications  
Gilbert Held. 
 - 7th ed. 
 - New Delhi :  Pearson Education,  c2002. 
 - xv, 765 p. :  ill. ;  23 cm. 
<br/><br/><label>ISBN: </label>0672322161 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Data transmission systems.<br/>Computer networks.
<br/><br/><label>Dewey Class. No.: </label>004.6