Information on the UCS Transformation Format 8 (UTF-8) is available at
http://www.stonehand.com/unicode/standard/utf8.html
An implementation is available at
ftp://ftp.super.org/pub/speech/celp_3.2a.tar.Z
An implementation is available from Jack Jansen at
ftp://ftp.cwi.nl/local/pub/audio/adpcm.shar
An implementation is available at
ftp://gaia.cs.umass.edu/pub/hgschulz/ccitt/ccitt_tools.tar.Z
A reference implementation was written by Carsten Borman and Jutta Degener (TU Berlin, Germany). It is available at
ftp://ftp.cs.tu-berlin.de/pub/local/kbs/tubmik/gsm/
An implementation is available at
ftp://parcftp.xerox.com/pub/net-research/lpc.tar.Z