^Dorpalen, Andreas (2015). Hindenburg and the Weimar Republic. Princeton, New Jersey. p. 68. ISBN 978-1-4008-7771-3. OCLC 927296753.{{cite book}}: CS1 maint: location missing publisher (link)
^Robert G.L. Waite, The Psychopathic God: Adolf Hitler, Basic Books, 1977, pp. 237–243
^Jon Jacobson, Locarno diplomacy: Germany and the west, 1925–1929 (2015).