Terminal equipment and protocols for telematic services : recommendations T.400 - T.418 / International Telecommunication Union
Terminal equipment and protocols for telematic services : recommendations T.431 - T.564 / International Telecommunication Union
Data communication networks : services and facilities, interfaces: recommendations X.1 - X.32 / International Telecommunication Union
Data communication networks : transmission, signalling and switching, network aspects, maintenance and administrative arrangements: recommendations X.40 - X.181 / International Telecommunication Union