MLA
Chase-Riboud, Barbara. Letter from Barbara Chase-Riboud (Paris, France) to Her Mother, Vivian May Chase (Philadelphia, Pennsylvania). Attached Is a Letter from David Riboud to His Grandmother, Vivian May Chase - July 14, 1974. 1974. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 8. https://digital.library.emory.edu/purl/757np5hr80-cor.
APA, 6th edition
Chase-Riboud, B. (1974). Letter from Barbara Chase-Riboud (Paris, France) to her mother, Vivian May Chase (Philadelphia, Pennsylvania). Attached is a letter from David Riboud to his grandmother, Vivian May Chase - July 14, 1974 (Box 1, Folder 8) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/757np5hr80-cor.
Chicago
Chase-Riboud, Barbara. “Letter from Barbara Chase-Riboud (Paris, France) to Her Mother, Vivian May Chase (Philadelphia, Pennsylvania). Attached Is a Letter from David Riboud to His Grandmother, Vivian May Chase - July 14, 1974.” Letters (correspondence). Barbara Chase-Riboud Papers, 1974. Box 1, Folder 8. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/757np5hr80-cor.