MLA
Barfield, John. Letter from John Barfield (near Dalton, Georgia) to His Wife. John Barfield Served in the 45th Alabama Infantry Regiment - June 4, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 19. https://digital.library.emory.edu/purl/7375tb2sdv-cor.
APA, 6th edition
Barfield, J. (1864). Letter from John Barfield (near Dalton, Georgia) to his wife. John Barfield served in the 45th Alabama Infantry Regiment - June 4, 1864 (Box 1, Folder 19) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/7375tb2sdv-cor.
Chicago
Barfield, John. “Letter from John Barfield (near Dalton, Georgia) to His Wife. John Barfield Served in the 45th Alabama Infantry Regiment - June 4, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 1, Folder 19. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/7375tb2sdv-cor.