Heuduck, A. a. W. (1949). Letter to Gerdt Wagner also Letter in German to Paul Heuduck, Janurary 26, 1949 and January 23, 1948. Saint Louis University Libraries Digitization Center.
Chicago-referens (17:e uppl.)Heuduck, Arno and Wagner. Letter to Gerdt Wagner Also Letter in German to Paul Heuduck, Janurary 26, 1949 and January 23, 1948. Saint Louis University Libraries Digitization Center, 1949.
MLA-referens (8:e uppl.)Heuduck, Arno and Wagner. Letter to Gerdt Wagner Also Letter in German to Paul Heuduck, Janurary 26, 1949 and January 23, 1948. Saint Louis University Libraries Digitization Center, 1949.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.