ETSI TR 101 085-1999 数字蜂窝通信系统(第2阶段).GSM增强型全速率(EFR)语音编解码器的性能特征GSM 06.55(版本7.0.0,1998年发布)
Digital Cellular Telecommunications System (Phase 2+); Performance Characterization of the GSM Enhanced Full Rate (EFR) Speech Codec GSM 06.55 Version 7.0.0 Release 1998