1. Mason, John Brown, Hitler's First Foes: A Study in Religion and Politics, Burges Publishing, Minneapolis:1936, 1.
2. Mason, 2.
3.http://www.newadvent.org/docs/pi11mb.htm
4.http://www.amazon.com/exec/obidos/ts/book-excerpt/0151002444/ref%3Dpm%5Fdp%5Fln%5Fb%5F1/104-5827254-9264467