MLA
Plummer, Harry L. Young Boy Standing next to a Puppy on a Stool Resting His Arm on the Stool. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6. https://digital.library.emory.edu/purl/12683bk3ps-cor.
APA, 6th edition
Plummer, H. L. Young boy standing next to a puppy on a stool resting his arm on the stool (Box 6) [Card photographs (photographs)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/12683bk3ps-cor.
Chicago
Plummer, Harry L. “Young Boy Standing next to a Puppy on a Stool Resting His Arm on the Stool.” Card photographs (photographs). Robert Langmuir African American Photograph Collection, n.d. Box 6. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/12683bk3ps-cor.