1998GSM 02.01-1998 Digital Cellular Telecommunications System (Phase 2+); Principles of Telecommunication Services Supported by a GSM Public Land Mobile Network (PLMN) (Version 5.3.0)
1996GSM 02.01-1996 Digital Cellular Telecommunications System (Phase 2+); Principles of Telecommunication Services Supported by a GSM Public Land Mobile Network (PLMN) (Version 5.1.0)