1. 3GPP TSGS-SA, Circuit Bearer Services (BS) Supported by a Public Land Mobile Network (PLMN), 3GPP TS 22.002 v. 3.6.0 (release 1999), 2001–03
2. 3GPP TSG-CN, Circuit Switched Multimedia Telephony, 3GPP TR 23.972 v.3.0.0 (release 1999), 2000–03
3. 3GPP TSG-CN, Mobile Radio Interface Layer 3 Specification; Core Network Protocols – Stage 3, 3GPP TS 24.008 v. 3.7.0 (release 1999), 2001–03
4. 3GPP TSGS-SA, Mandatory Speech Codec Speech Processing Functions. AMR Speech Codec; General Description, 3GPP TS 26.071 v. 3.0.1 (release 1999), 1999–08
5. 3GPP TSGS-SA, Codec for Circuit Switched Multimedia Telephony Service; General Description, 3GPP TS 26.110 v. 3.0.1 (release 1999), 1999–08