Schneider, Helmut (1936). Flugzeug-Typenbuch 1936(PDF) (in German) (1936 ed.). Leipzig: Herm. Beyer Verlag. p. 13. Archived from the original(PDF) on 2018-09-08. Retrieved 2018-12-21.
flightglobal.com
"The B.F.W. M.20". Flight: 914–916. 18 October 1928. Retrieved 23 September 2017.
web.archive.org
Schneider, Helmut (1936). Flugzeug-Typenbuch 1936(PDF) (in German) (1936 ed.). Leipzig: Herm. Beyer Verlag. p. 13. Archived from the original(PDF) on 2018-09-08. Retrieved 2018-12-21.