Information on Drawing in Perspective   

http://www.olejarz.com/arted/perspective/

http://www.sanford-artedventures.com/create/tech_1pt_perspective.html

http://mathforum.org/sum95/math_and/perspective/perspect.html

perspective and values http://www2.evansville.edu/studiochalkboard/draw.html

http://www.cs.appstate.edu/~sjg/class/1010/wc/geom/perspective/