ETSI GSM 04.80-1994 European Digital Cellular Telecommunications System (Phase 2); Mobile Radio Interface Layer 3 Supplementary Services Specification Formats and Coding
1996ETSI GSM 04.80-1996 Digital Cellular Telecommunications System (Phase 2+); Mobile Radio Interface Layer 3 Supplementary Services Specification Formats and Coding
1994ETSI GSM 04.80-1994 European Digital Cellular Telecommunications System (Phase 2); Mobile Radio Interface Layer 3 Supplementary Services Specification Formats and Coding