MLA
Doubleday. Bill Pickett, Famous Negro Cowboy. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 71. https://digital.library.emory.edu/purl/443nvx0k9v-cor.
APA, 6th edition
D. Bill Pickett, famous negro cowboy (Box 71) [Photographic postcards]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/443nvx0k9v-cor.
Chicago
Doubleday. “Bill Pickett, Famous Negro Cowboy.” Photographic postcards. Robert Langmuir African American Photograph Collection, n.d. Box 71. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/443nvx0k9v-cor.