Here is a rather remote/difficult book find that is a bit controversial.  It is effectively banned by not being printed for some reason.  The book describes how United States financial and manufacturing people helped finance Hitler’s beginnings.

Book Title: De geldbronnen van het Nationaal-Socialisme: drie gesprekken met Hitler

http://www.jrbooksonline.com/PDF_Books/Warburg_Hitler%27s%20Secret%20Backers.pdf