MLA
Latimer, Thomas H. Letter from Thomas H. Latimer (Headquarters, Camp Direction, Macon, Georgia) to "Dear Friend and Brother" - October 20, 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 4, Folder 37. https://digital.library.emory.edu/purl/508hdr7tq2-cor.
APA, 6th edition
Latimer, T. H. (1862). Letter from Thomas H. Latimer (Headquarters, Camp Direction, Macon, Georgia) to "Dear Friend and Brother" - October 20, 1862 (Box 4, Folder 37) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/508hdr7tq2-cor.
Chicago
Latimer, Thomas H. “Letter from Thomas H. Latimer (Headquarters, Camp Direction, Macon, Georgia) to ‘Dear Friend and Brother’ - October 20, 1862.” Letters (correspondence). Civil War Collection, 1862. Box 4, Folder 37. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/508hdr7tq2-cor.