MLA
Witzel. A Portrait of Billy Mason : an African American Man in a Suit and Hat. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 74. https://digital.library.emory.edu/purl/617qnk98w3-cor.
APA, 6th edition
W. A portrait of Billy Mason : an African American man in a suit and hat (Box 74) [Postcards]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/617qnk98w3-cor.
Chicago
Witzel. “A Portrait of Billy Mason : an African American Man in a Suit and Hat.” Postcards. Robert Langmuir African American Photograph Collection, n.d. Box 74. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/617qnk98w3-cor.