ETSI TS 124 525-2015 Universal Mobile Telecommunications System (UMTS); LTE; Business trunking; Architecture and functional description (V12.1.0; 3GPP TS 24.525 version 12.1.0 Release 12)
2017ETSI TS 124 525-2017 Universal Mobile Telecommunications System (UMTS); LTE; Business trunking; Architecture and functional description (V14.0.0; 3GPP TS 24.525 version 14.0.0 Release 14)
2015ETSI TS 124 525-2015 Universal Mobile Telecommunications System (UMTS); LTE; Business trunking; Architecture and functional description (V12.1.0; 3GPP TS 24.525 version 12.1.0 Release 12)