MLA
Speir, James H. Letter from James H. Speir to "Dear Sister" - August 3, 1863. 1863. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 53. https://digital.library.emory.edu/purl/515bcc2gf9-cor.
APA, 6th edition
Speir, J. H. (1863). Letter from James H. Speir to "Dear Sister" - August 3, 1863 (Box 6, Folder 53) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/515bcc2gf9-cor.
Chicago
Speir, James H. “Letter from James H. Speir to ‘Dear Sister’ - August 3, 1863.” Letters (correspondence). Civil War Collection, 1863. Box 6, Folder 53. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/515bcc2gf9-cor.