Understanding data communications / 
George E. Friend and others. 
 - 2nd ed. 
 - Indiana :  Howard W. Sams and company,  1989. 
<br/><br/><label>ISBN: </label>0672272709 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Data transmission systems
<br/><br/><label>LC Class. No.: </label>TK5105.5  / Und 1989