Schwager, M. (1949). Letter to Paul Heuduck, October 5, 1949. Saint Louis University Libraries Digitization Center.
Chicago-referens (17:e uppl.)Schwager, Mortimer. Letter to Paul Heuduck, October 5, 1949. Saint Louis University Libraries Digitization Center, 1949.
MLA-referens (8:e uppl.)Schwager, Mortimer. Letter to Paul Heuduck, October 5, 1949. Saint Louis University Libraries Digitization Center, 1949.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.