MLA
Art Photo Greeting Co. (Elizabeth, N.J.). The whipping post, Dover, Del. : African American man being whipped with crowd watching. unknown. Robert Langmuir African American Photograph Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/105s7h44n1-cor.
APA, 6th edition
Art Photo Greeting Co. (Elizabeth, N.J.). (unknown)[The whipping post, Dover, Del. : African American man being whipped with crowd watching]. Robert Langmuir African American Photograph Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/105s7h44n1-cor.
Chicago
Art Photo Greeting Co. (Elizabeth, N.J.), The whipping post, Dover, Del. : African American man being whipped with crowd watching, unknown, Robert Langmuir African American Photograph Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/105s7h44n1-cor.