MLA
Howard, Tazewell M. Letter from Tazewell M. Howard to His Brother, Dr. Thomas Henry Howard. Tazewell Howard Served as a Surgeon in the 55th Georgia Infantry Regiment - August 14, 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 3, Folder 64. https://digital.library.emory.edu/purl/95269p8f10-cor.
APA, 6th edition
Howard, T. M. (1862). Letter from Tazewell M. Howard to his brother, Dr. Thomas Henry Howard. Tazewell Howard served as a surgeon in the 55th Georgia Infantry Regiment - August 14, 1862 (Box 3, Folder 64) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/95269p8f10-cor.
Chicago
Howard, Tazewell M. “Letter from Tazewell M. Howard to His Brother, Dr. Thomas Henry Howard. Tazewell Howard Served as a Surgeon in the 55th Georgia Infantry Regiment - August 14, 1862.” Letters (correspondence). Civil War Collection, 1862. Box 3, Folder 64. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/95269p8f10-cor.