This interview with a wig seller explains about virgin European hair and other hair types, how wigs are made, why hair knots and how... It's more in depth than most other stuff I've read about hair. The Follea blog has a lot of info as well. If you have different/more info, please share.
http://askchavi.blogspot.ca/2012/06/interview-with-isadore-sternhil...