Digital cellular telecommunications system (Phase 2+); Mobile radio interface layer 3; Supplementary services specification; General aspects (3GPP TS 04.10 version 7.1.0 Release 1998)
Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); Circuit Bearer Services (BS) supported by a Public Land Mobile Network (PLMN) (3GPP TS 22.002 version 16.0.0 Release 16)
Universal Mobile Telecommunications System (UMTS); General Universal Mobile Telecommunications System (UMTS) architecture (3GPP TS 23.101 version 15.0.0 Release 15)