MLA
Valentine, and Sons. The Colonnade, Hotel Royal Poinciana, Palm Beach, Fla. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 71. https://digital.library.emory.edu/purl/829b5mkm1f-cor.
APA, 6th edition
V., & S. The Colonnade, Hotel Royal Poinciana, Palm Beach, Fla. (Box 71) [Postcards]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/829b5mkm1f-cor.
Chicago
Valentine, and Sons. “The Colonnade, Hotel Royal Poinciana, Palm Beach, Fla.” 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/829b5mkm1f-cor.