MLA
Valentine, and Sons. Lake Hollingsworth, Lakeland, Fla. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 71. https://digital.library.emory.edu/purl/5805x69pd7-cor.
APA, 6th edition
V., & S. Lake Hollingsworth, Lakeland, Fla. (Box 71) [Postcards]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/5805x69pd7-cor.
Chicago
Valentine, and Sons. “Lake Hollingsworth, Lakeland, 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/5805x69pd7-cor.