Is there a comprehensive XSL tutorial on the net?

Hello Folks,

I need a comprehensive tutorial on XSL on the net as
this current school project of mine requires me to
generate schema conforming xml document dynamically.

If anyone know of such a link in which the tutorial
talks about advance XSL feature such as variables etc,
I would appreciate it greatly if you could provide me
with it. 

Thank you.

Rgds,
Javier

__________________________________________________
Do You Yahoo!?
Yahoo! Shopping - Beat the crowds!  Do your X'mas Shopping Online!
http://shopping.yahoo.com.sg/