Raytracing manual

[Kadri]

http://static.yafaray.org/guide/yafaray_course_english.pdf
              (ıt is a direct link to the pdf as you see)

It is more general  about raytracing , GI (and Yafaray) ...
I found it very informative .

Cheers.

Kadri.

[Henry Blewer]

This is a very good article. I read it a while back. It has some useful information on GI in general for any app.