1. 32kb/s ADPCM;CCITT Recommendation G.721,1984
2. Two approaches for waveform coding of 9.6kb/s voiceband data signals through 32kb/s ADPCM;Bevenuto;IEEE Trans. Commun.,1988
3. Adaptive Differential Pulse Code Modulation System;Shampiro,1989
4. 40, 32,24,16 Kb/s ADPCM;CCITT Recommendation G.726,1990
5. 5-,4-,3-,2- Bit/sample Embedded ADPCM;CCITT Recommendation G.727,1990