Kessler, Gary C..  <br/><br/>
ISDN Concepts Facilities and Services /   1 t. 
Kessler Gary C., Southwick Peter V.. 
 - Signature 4 edition. 
 - New York :   McGraw-Hill,   1998. 
 - XXVII, 3 s.:   il.;   24 cm. 
<br/><br/><label>ISBN: </label>007034437X