Kristine Washburn contributed reference to this site devoted
to (one person's work in) 
<A HREF ="http://math1.uibk.ac.at/~werner/light/"> advanced raytracing. </A> 

<p>
Jim Asbury contributed reference to this site devoted
to some 
<A HREF ="http://www.acm.org/crossroads/xrds3-4/raytracing.html">
elementary remarks </A>  on ray-tracing, which overlap with the
remarks in the text.

<p>
Some sample
<A HREF ="http://www.geocities.com/stormbringer777/CPlusPlus.html">
		files  </A> by Nick Demos, doing some of the
		same jobs as the professor's prototype files.
		No guarantees; use at your own risk. Thanks, Nick.
		Fall 2000.

<p>
<A HREF ="hous.ps"> Ray tracing picture  </A> by John Houston.

<p>
<A HREF ="http://www.cs.utah.edu/~shirley/papers/"> Website on ray-tracing </A>
	of Prof Shirley, University of Utah. Recommended by Nick Demos,
	November, 2000.