1. Pulse code modulation (PCM) of voice frequencies. ITU-T Recommendation G.711, 1988.
2. 7 KHz audio-coding within 64 kbps. ITU-T Recommendation G.722, 1988.
3. . Code-excited linear prediction (CELP): High-quality speech at very low bit rates. Proc IEEE ICASSP'85, p 937–940.
4. , , , . Structure of a 16 kbit/s base codec for wideband speech encoding with QoS controls. ASJ Proc, 1-8-1, September 1988.
5. , , , . Realizing tone quality and bandwidth scalability for wideband speech encoding with QoS controls. ASJ Proc, 1-8-2, September 1988.