MLA
Wilson, W. W. Letter from W. W. Wilson to Mr. Brown. Wilson, a Surgeon, Served in the 35th Georgia Infantry Regiment - June 4, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 7, Folder 36. https://digital.library.emory.edu/purl/160cvdndkr-cor.
APA, 6th edition
Wilson, W. W. (1864). Letter from W. W. Wilson to Mr. Brown. Wilson, a surgeon, served in the 35th Georgia Infantry Regiment - June 4, 1864 (Box 7, Folder 36) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/160cvdndkr-cor.
Chicago
Wilson, W. W. “Letter from W. W. Wilson to Mr. Brown. Wilson, a Surgeon, Served in the 35th Georgia Infantry Regiment - June 4, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 7, Folder 36. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/160cvdndkr-cor.