MLA
Chase-Riboud, Barbara. Letter from Barbara Chase-Riboud (Paris, France) to Her Mother, Vivian May Chase (Philadelphia, Pennsylvania) - 1968. 1968. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 5. https://digital.library.emory.edu/purl/52259zw4js-cor.
APA, 6th edition
Chase-Riboud, B. (1968). Letter from Barbara Chase-Riboud (Paris, France) to her mother, Vivian May Chase (Philadelphia, Pennsylvania) - 1968 (Box 1, Folder 5) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/52259zw4js-cor.
Chicago
Chase-Riboud, Barbara. “Letter from Barbara Chase-Riboud (Paris, France) to Her Mother, Vivian May Chase (Philadelphia, Pennsylvania) - 1968.” Letters (correspondence). Barbara Chase-Riboud Papers, 1968. Box 1, Folder 5. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/52259zw4js-cor.