2000ETSI EN 300 937:2000 Digital Cellular Telecommunications System (Phase 2+); Data Link (DL) Layer; General Aspects (GSM 04.05 Version 8.0.1 Release 1999)
1999ETSI EN 300 937-1999 Digital Cellular Telecommunications System (Phase 2+); Data Link (DL) Layer; General Aspects GSM 04.05 Version 6.0.1 Release 1997