MLA
Davis, Susan. Letter from Susan Davis (West Point, Georgia) to "Dear Charles" - July 31, 1865 (Photocopy). 1865. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 3, Folder 2. https://digital.library.emory.edu/purl/945cc2fs0f-cor.
APA, 6th edition
Davis, S. (1865). Letter from Susan Davis (West Point, Georgia) to "Dear Charles" - July 31, 1865 (photocopy) (Box 3, Folder 2) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/945cc2fs0f-cor.
Chicago
Davis, Susan. “Letter from Susan Davis (West Point, Georgia) to ‘Dear Charles’ - July 31, 1865 (Photocopy).” Letters (correspondence). Civil War Collection, 1865. Box 3, Folder 2. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/945cc2fs0f-cor.