MLA
Fowler, John W. Letter from John W. Fowler (Camp near Fairfax Court House, Virginia) Attesting to the Military Service of Ezekiel A. Davis - October 14, 1861. 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 3, Folder 27. https://digital.library.emory.edu/purl/252j6q583x-cor.
APA, 6th edition
Fowler, J. W. (1861). Letter from John W. Fowler (camp near Fairfax Court House, Virginia) attesting to the military service of Ezekiel A. Davis - October 14, 1861. (Box 3, Folder 27) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/252j6q583x-cor.
Chicago
Fowler, John W. “Letter from John W. Fowler (Camp near Fairfax Court House, Virginia) Attesting to the Military Service of Ezekiel A. Davis - October 14, 1861.” Letters (correspondence). Civil War Collection, 1861. Box 3, Folder 27. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/252j6q583x-cor.