Universal Decimal Classification :  UDC 654 : telecommunication services : organization, administration and operation 

 - 4. ed 
 - 11 p. 
 - FID publication ; n.179 .
<br/><br/><label>ISBN: </label>0-580-05039-4 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Telecomunicações
<br/><br/><label>Universal Decimal Class. No.: </label>025.45CDU  / F293u