Unfortunately, perhaps because of the verisimilitude of the disciplines needed to make a film like Star Wars come together, the making-of narrative is surprisingly fragmented and often incomplete. A quick look at the bibliography needed to put together this post should give a good idea of just how fragmented. And once you’re down the rabbit hole, you quickly learn that nothing found there can be taken at face value. Quotes, drawings, photos and diagrams lack sources, are undated, some old, some new, some so distorted as to be pure fiction and most of it entirely out of context.
Heilemann's research is quite thorough, and fascinating as well. http://binarybonsai.com/2010/09/18/george-lucas-stole-chewbacca-but-its-okay/ (via Boing Boing)