MLA
Co., E. C. Kropp. Three Chocolate Drops- Down in Sunny Dixie : Three African American Boys Sitting on a Fence. 1950. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 73. https://digital.library.emory.edu/purl/030prr4xjn-cor.
APA, 6th edition
Co., E. C. K. (1950). Three chocolate drops- Down in Sunny Dixie : three African American boys sitting on a fence (Box 73) [Postcards]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/030prr4xjn-cor.
Chicago
Co., E. C. Kropp. “Three Chocolate Drops- Down in Sunny Dixie : Three African American Boys Sitting on a Fence.” Postcards. Robert Langmuir African American Photograph Collection, 1950. Box 73. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/030prr4xjn-cor.