1Chong Kwan Un, Hwang Soo Lee. A Study of the Comparative Performance of Adaptive Delta Modulation Systems[J]. IEEE Transactions On Communications,1980, Com-28(1):96-102.
2Vanoy C Welch, Thomas E Trcmain, Joseph P Campbell,Jr. A Comparison of US GovernmcntStandard Voice Coders[J]. IEEE CH2681-51891-0269,1989: 269-273.