Held, Gilbert. <br/><br/>
Understanding data communications / 
Gilbert Held. 
 - 7th. 
 - Delhi :  Pearson Education,  2003. 
 - xv, 765 pages :  illustrations. 
<br/><br/> Includes index. 
<br/><br/><label>ISBN: </label>8129702118 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Data Transimission systems.<br/>Computer networks.<br/>Computer networks.