CCITT <br/><br/>
BLUE BOOK,VOLUME VI,FASCICLE VI.3: SPECIFICATIONS OF SIGNALLING SYSTEM NO 6,RECOMMENDATIONS Q.251 - Q 

 - GENEVA  ITU  1989 
 -  152 
<br/><br/> SC-021 
<br/><br/><label>ISBN: </label>ERNET 
<br/><br/><label>Dewey Class. No.: </label>335