MLA
Howe, F. L. Mule Race, Here Comes De Winner : African American Boys on a Fence. 1906. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 72. https://digital.library.emory.edu/purl/549g4f4qtd-cor.
APA, 6th edition
Howe, F. L. (1906). Mule race, here comes de winner : African American boys on a fence (Box 72) [Postcards]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/549g4f4qtd-cor.
Chicago
Howe, F. L. “Mule Race, Here Comes De Winner : African American Boys on a Fence.” Postcards. Robert Langmuir African American Photograph Collection, 1906. Box 72. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/549g4f4qtd-cor.