Held, Gilbert <br/><br/>
Understanding data communications/ 
by. Gilbert Held 
 - U.S.A.:  Sams Publishing,  c1996. 
 - xv, 504p.:  ill.;  23.3cm. 
<br/><br/> Includes glossary  bibliography and  index. 
<br/><br/><label>ISBN: </label>0-672-30934-3 
<br/><br/><label>Dewey Class. No.: </label>B.C. 004.6  / Un22