Integrated services digital network (ISDN) : general structure and service capabilities: recommendations I.110 - I.257 / International Telecommunication Union
Integrated services digital network (ISDN) : overall network aspects and functions, ISDN user-network interfaces: recommendations I.310 - I.470 / International Telecommunication Union
General maintenance principles : maintenance of international transmission systems and telephone circuits: recommendations M.10 - M.782 / International Telecommunication Union
Maintenance of international telegraph, phototelegraph and leased circuits : maintenance of the international public telephone network: maintenance of maritime satellite and data transmission systems: recommendations M.800 - M.1375 / International Telecommunication Union