ETSI TS 100 975 Digital cellular telecommunications system (Phase 2+) (GSM); Interworking between a Public Land Mobile Network (PLMN) and a Packet Switched Public Data Network/Integrated Services Digital Network (PSPDN/ISDN) for the support of packet switched data transmission services (GSM 09.06 version 7.0.0 Rele

standard by European Telecommunications Standards Institute, 08/01/1999