Hi, I just have a lil problem. 
I'm always extending my cel explanation page at 
http://home.arcor.de/cels/CelHP/cel_begriffe.htm 
(sorry, in german only), and at the moment I just 
can't find out what book cels are. 
Can someone help me out?
And if you have the remaining (hope that's the 
right word), to check the site out, are there cel 
types I haven't explained yet?