I am sure to mess up Wikipedia protocols until I learn more of the ropes. And that probably goes for this post. It seems that my current project of editing "Perspective projection distortion" needs my attention. One criticism appears to be regarding the Introduction. There was no heading Introduction when I started and which surprised me but it can be more or less seamlessly created with material already in the article. I will attempt to do so forthwith. There was also an allusion to my referencing my own work, i.e., http://www.scribd.com/robert_kelso_2, but which entails new science and is the only reference for the purpose used. I welcome your further input.   Pat Kelso