MLA
The Happiest People on Earth : an African American Man and Woman Outside, with a Cotton Field behind Them [Hand Colored]. 1911. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 68. https://digital.library.emory.edu/purl/3009w0vt7b-cor.
APA, 6th edition
The happiest people on earth : an African American man and woman outside, with a cotton field behind them [hand colored] (Box 68). (1911). [Postcards]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/3009w0vt7b-cor.
Chicago
“The Happiest People on Earth : an African American Man and Woman Outside, with a Cotton Field behind Them [Hand Colored].” Postcards. Robert Langmuir African American Photograph Collection, 1911. Box 68. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/3009w0vt7b-cor.