The joint revision to POSIX and the Single UNIX Specification have received international approval by the ISO/IEC and have become International Standard ISO/IEC 9945:2002.
See http://www.unix.org/version3/ for information on the specification, including how to read and/or download a free copy of the standard
See the ISO announcement at:
http://www.iso.ch/iso/en/commcentre/pressreleases/2002/Ref837.html