MLA
Boxcars That Say Ringling Bros. and Barnum & Bailey Combined Shows. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 7. https://digital.library.emory.edu/purl/235gb5mkrx-cor.
APA, 6th edition
Boxcars that say Ringling Bros. and Barnum & Bailey Combined Shows (Box 7). [Black-and-white photographs]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/235gb5mkrx-cor.
Chicago
“Boxcars That Say Ringling Bros. and Barnum & Bailey Combined Shows.” Black-and-white photographs. Robert Langmuir African American Photograph Collection, n.d. Box 7. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/235gb5mkrx-cor.