MLA
Cottingham, P. D., and Co. Sampson Harmon, Sampson Hat. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 72. https://digital.library.emory.edu/purl/890rr4xh0p-cor.
APA, 6th edition
Cottingham, P. D., & C. Sampson Harmon, Sampson Hat (Box 72) [Photographic postcards]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/890rr4xh0p-cor.
Chicago
Cottingham, P. D., and Co. “Sampson Harmon, Sampson Hat.” Photographic postcards. Robert Langmuir African American Photograph Collection, n.d. Box 72. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/890rr4xh0p-cor.