MLA
Co., E. C. Kropp. Sunday Afternoon : down in Sunny Dixie. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 69. https://digital.library.emory.edu/purl/699n2z34xs-cor.
APA, 6th edition
Co., E. C. K. Sunday afternoon : down in sunny Dixie (Box 69) [Postcards]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/699n2z34xs-cor.
Chicago
Co., E. C. Kropp. “Sunday Afternoon : down in Sunny Dixie.” Postcards. Robert Langmuir African American Photograph Collection, n.d. Box 69. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/699n2z34xs-cor.