MLA
Souvenir Post Card Co. (N.Y.). De 'Possum Hunt Treed : two African Americans and a dog hunting an opossum. unknown. Robert Langmuir African American Photograph Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/99351c5b48-cor.
APA, 6th edition
Souvenir Post Card Co. (N.Y.). (unknown)[De 'Possum Hunt Treed : two African Americans and a dog hunting an opossum]. Robert Langmuir African American Photograph Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/99351c5b48-cor.
Chicago
Souvenir Post Card Co. (N.Y.), De 'Possum Hunt Treed : two African Americans and a dog hunting an opossum, unknown, Robert Langmuir African American Photograph Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/99351c5b48-cor.