[1] ISO
http://www.iso.ch/iso/en/ittf/c040611_ISO_IEC_TR_21000-1_2004(E).zip
The first part of the ISO specification. Describes work done as well as future developments.
[2] Bormans J. and Hill K., "MPEG-21 Overview v.5"
http://www.chiariglione.org/mpeg/standards/mpeg-21/mpeg-21.htm
An overview of the ISO paper above.
[3]
Burnett I., Van de Walle R., Hill K., Bormans J., and Pereira F. "MPEG-21:
Goals and
Achievements"
http://www.chiariglione.org/mpeg/events&tutorials/MMpaper.pdf
A more reader-friendly journal article.
[4] "Welcome to enikos - The power of MPEG 21"
Company based in Wollongong Australia that employs Ian Burnett as CTO, who is an active participant in ISO MPEG 21 work.