General aspects of digital transmission systems : terminal equipments: recommendations G.700 - G.795 / International Telecommunication Union
Digital networks, digital sections and digital line systems : recommendations G.801 - G.961 / International Telecommunication Union
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