1. 40, 32, 24, 16 kb/s ADPCM, CCITT Recommendation G.726-1990.
2. Coding of speech at 8 kb/s using conjugate structure algebraic code excited linear prediction (CSACELP), ITU-T Recommendation G.729-1996.
3. W. Chu, Speech Coding Algorithms: Foundation and Evolution of Standardized Coders (John Wiley & Sons Inc., New York, 2003).
4. W. C. Chu, “A scalable MELP coder based on embedded quantization of the line spectral frequencies,” in Proc. of Int. Symp. on Intelligent Signal Processing and Communication Systems, ISPACS, 13–16 Dec. 2005, Hong Kong (2005), pp. 29–32. DOI: 10.1109/ISPACS.2005.1595338.
5. S. Dusan, J. L. Flanagan, A. Karve, M. Balaraman, “Speech compression by polynomial approximation,” IEEE Trans. Audio, Speech, Language Process. 15, No. 2, 387 (2007). DOI: 10.1109/TASL.2006.881705.