MLA
Illustrated Post Card Co. (N.Y.). Black guard : a row of African American boys [hand colored]. unknown. Robert Langmuir African American Photograph Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/672b8gthwk-cor.
APA, 6th edition
Illustrated Post Card Co. (N.Y.). (unknown)[Black guard : a row of African American boys [hand colored]]. Robert Langmuir African American Photograph Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/672b8gthwk-cor.
Chicago
Illustrated Post Card Co. (N.Y.), Black guard : a row of African American boys [hand colored], unknown, Robert Langmuir African American Photograph Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/672b8gthwk-cor.