ETSI TS 122 091-2001 数字蜂窝通信系统(第2+阶段)(GSM).全球移动通信系统(UMTS).显式呼叫转移(ECT).3GPP TS 22.091(版本4.0.0,第4次发布)
Digital Cellular Telecommunications System (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); Explicit Call Transfer (ECT) 3GPP TS 22.091 Version 4.0.0 Release 4