MLA
Harrison, Nancy. Letter from Nancy Harrison (Carroll County, Georgia) to "Dear Father" - September 17, 1851 (Photocopy). 1851. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 4, Folder 50. https://digital.library.emory.edu/purl/358bg79dn9-cor.
APA, 6th edition
Harrison, N. (1851). Letter from Nancy Harrison (Carroll County, Georgia) to "Dear Father" - September 17, 1851 (photocopy) (Box 4, Folder 50) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/358bg79dn9-cor.
Chicago
Harrison, Nancy. “Letter from Nancy Harrison (Carroll County, Georgia) to ‘Dear Father’ - September 17, 1851 (Photocopy).” Letters (correspondence). Civil War Collection, 1851. Box 4, Folder 50. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/358bg79dn9-cor.