Peter Shirley Brian E. Smits Helen H. Hu Eric P. Lafortune A practitioners' assessment of light reflection models. 40- 1997 conf/pg/1997 Pacific Conference on Computer Graphics and Applications http://csdl.computer.org/comp/proceedings/pg/1997/8028/00/80280040abs.htm db/conf/pg/pg1997.html#ShirleySHL97