Used websites:

Several pictures and tekst that were used came from this website that once belonged to Dennis en Jomy.
http://www.koisite.eu/
Airlift was learned from our Belgian koi friends; 
http://www.airlift.be/
http://users.telenet.be/airlift/

http://www.elfwdr.nl/vijver/filter.htm

KHV From the (ex) site from Jurdim.
http://www.khvinfo.nl/index.php?categoryid=1

Koiforum:
http://www.koiforum.nl/
http://www.koivrienden.be/phpBB/portal.php
http://forum.nvn-koi.nl/

Commercial sites I got info from.
http://www.koikarper.nl/
http://www.aenc-koi.nl/index.htm
http://www.dekoi.info/anatomie.html

Also some info was used thas was printed in the magazine KOI from the largest Dutch KOI society. The organizers of the largest KOI show on earth.
www.nvn-koi.nl

All the rest is from my own experience and work knowledge being a medical parasitological research analist.