MLA
Chase-Riboud, Barbara. Letter from Barbara Chase-Riboud to Her Mother, Vivian May Chase (Philadelphia, Pennsylvania) - December 13, 1981. 1981. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 9. https://digital.library.emory.edu/purl/00000000vd-cor.
APA, 6th edition
Chase-Riboud, B. (1981). Letter from Barbara Chase-Riboud to her mother, Vivian May Chase (Philadelphia, Pennsylvania) - December 13, 1981 (Box 1, Folder 9) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/00000000vd-cor.
Chicago
Chase-Riboud, Barbara. “Letter from Barbara Chase-Riboud to Her Mother, Vivian May Chase (Philadelphia, Pennsylvania) - December 13, 1981.” Letters (correspondence). Barbara Chase-Riboud Papers, 1981. Box 1, Folder 9. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/00000000vd-cor.