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-viite (17. p.)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-viite (8. p.)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.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.