Schwager, M. (1947). Letter to Arno Heuduck, December 29, 1947. Saint Louis University Libraries Digitization Center.
Čikaški stil citiranja (17. izdanje)Schwager, Mortimer. Letter to Arno Heuduck, December 29, 1947. Saint Louis University Libraries Digitization Center, 1947.
MLA način citiranja (8. izdanje)Schwager, Mortimer. Letter to Arno Heuduck, December 29, 1947. Saint Louis University Libraries Digitization Center, 1947.
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