MLA
Swann, Henry C. Letter from Henry C. Swann (Manassas Junction) to "Miss Lid.��� Swann Was a Confederate Soldier, Probably from Alabama - January 1, 1862 (Typescript). 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 40. https://digital.library.emory.edu/purl/409j3tx9vv-cor.
APA, 6th edition
Swann, H. C. (1862). Letter from Henry C. Swann (Manassas Junction) to "Miss Lid.��� Swann was a Confederate soldier, probably from Alabama - January 1, 1862 (typescript) (Box 6, Folder 40) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/409j3tx9vv-cor.
Chicago
Swann, Henry C. “Letter from Henry C. Swann (Manassas Junction) to ‘Miss Lid.��� Swann Was a Confederate Soldier, Probably from Alabama - January 1, 1862 (Typescript).” Letters (correspondence). Civil War Collection, 1862. Box 6, Folder 40. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/409j3tx9vv-cor.