Held, Gilbert. <br/><br/>
Understanding data communications / 
Gilbert Held. 
 - 3rd ed. 
 - Indiana, USA  SAMS  1991 
 - 368 pages :  illustrations ;  23.5 cm 
<br/><br/> Includes index 
<br/><br/>Includes bibliographical references (pages 349 - 350) and index 
<br/><br/><label>ISBN: </label>0672300052 
<br/><br/><label>Subjects--Topical Terms: </label><br/>communications