MLA
A Dark Subject : Boys and Young Men Sitting on Steps, One Holding a Baseball Bat. 1896. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 5. https://digital.library.emory.edu/purl/112m63xsq6-cor.
APA, 6th edition
A dark subject : boys and young men sitting on steps, one holding a baseball bat (Box 5). (1896). [Black-and-white photographs]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/112m63xsq6-cor.
Chicago
“A Dark Subject : Boys and Young Men Sitting on Steps, One Holding a Baseball Bat.” Black-and-white photographs. Robert Langmuir African American Photograph Collection, 1896. Box 5. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/112m63xsq6-cor.