Tim Norman wrote the original pbm2ppa filter.
Giorgio Marzano wrote most of the pnm2ppa work post-May 1999
Andrew van der Stock fixed many bugs, and coded many, many lines. He also spell-checked this HOWTO and corrected some wrong information.
Klamer Schutte wrote the calibration mechanism and files.
Duncan Haldane is the Red Hat port master. He made spell-checking too ;-)
Someone (please, if it has been you, email me) made DEB packages.
The whole ppa.devel@listbot.com mail list helped in the development of the new versions, testing software and reporting bugs.
Daniel Payno told me to make a HOWTO to help his friends installing an HP720C, so he is the guilty of this document.