MLA
Rotograph Co. (New York, N.Y.). Paul Laurence Dunbar, an African American poet, sitting on a chair holding a book, while wearing a suit. unknown. Robert Langmuir African American Photograph Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/559q2bvqbb-cor.
APA, 6th edition
Rotograph Co. (New York, N.Y.). (unknown)[Paul Laurence Dunbar, an African American poet, sitting on a chair holding a book, while wearing a suit]. Robert Langmuir African American Photograph Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/559q2bvqbb-cor.
Chicago
Rotograph Co. (New York, N.Y.), Paul Laurence Dunbar, an African American poet, sitting on a chair holding a book, while wearing a suit, unknown, Robert Langmuir African American Photograph Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/559q2bvqbb-cor.