Wagner, G. (1940). Letter in German to Paul Heuduck, February 12, 1940. Saint Louis University Libraries Digitization Center.
Chicago-viite (17. p.)Wagner, Gerdt. Letter in German to Paul Heuduck, February 12, 1940. Saint Louis University Libraries Digitization Center, 1940.
MLA-viite (8. p.)Wagner, Gerdt. Letter in German to Paul Heuduck, February 12, 1940. Saint Louis University Libraries Digitization Center, 1940.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.