MLA
Hook, W. R. A Gathering of the Ku Klux Klan with a Cross in the Middle. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 58. https://digital.library.emory.edu/purl/201bk3j9rb-cor.
APA, 6th edition
Hook, W. R. A gathering of the Ku Klux Klan with a cross in the middle (Box 58) [Card photographs (photographs)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/201bk3j9rb-cor.
Chicago
Hook, W. R. “A Gathering of the Ku Klux Klan with a Cross in the Middle.” Card photographs (photographs). Robert Langmuir African American Photograph Collection, n.d. Box 58. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/201bk3j9rb-cor.