MLA
Chase-Riboud, Barbara. Telegram Sent by Barbara Chase-Riboud to Her Mother and Grandmother (Philadelphia, Pennsylvania) Wishing Them a Happy Mother's Day. 1964. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 3. https://digital.library.emory.edu/purl/023vt4b99q-cor.
APA, 6th edition
Chase-Riboud, B. (1964). Telegram sent by Barbara Chase-Riboud to her mother and grandmother (Philadelphia, Pennsylvania) wishing them a happy Mother's Day (Box 1, Folder 3) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/023vt4b99q-cor.
Chicago
Chase-Riboud, Barbara. “Telegram Sent by Barbara Chase-Riboud to Her Mother and Grandmother (Philadelphia, Pennsylvania) Wishing Them a Happy Mother's Day.” Letters (correspondence). Barbara Chase-Riboud Papers, 1964. Box 1, Folder 3. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/023vt4b99q-cor.