Integrated Services Digital Network (ISDN) - Interworking between public ISDNs and private ISDNs for the provision of telecommunication services - General aspects; English version ETS 300345:1995
Integrated Services Digital Network (ISDN) - Signalling System No.7 (SS7) - ISDN User Part (ISUP) version 4 for the international interface - Part 20: Completion of Calls on No Reply (CCNR) supplementary service [ITU-T Recommendation Q.733, clause 5 (1999), modified]
Telecommunications Management Network (TMN) - Functional specification of Customer Administration (CA) on the Operations System/Network Element (OS/NE) interface - Part 1: Single line configurations
Integrated Services Digital Network (ISDN) - Selective Call Forwarding (SCF) supplementary services (unconditional, busy and no reply) - Service description
