MLA
Brandon, William Joseph. Letter from William Joseph Brandon (Camp near Fredericksburg, Virginia) to "Folks at Home" - December 7, 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 34. https://digital.library.emory.edu/purl/699n2z35wg-cor.
APA, 6th edition
Brandon, W. J. (1862). Letter from William Joseph Brandon (camp near Fredericksburg, Virginia) to "Folks at Home" - December 7, 1862 (Box 1, Folder 34) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/699n2z35wg-cor.
Chicago
Brandon, William Joseph. “Letter from William Joseph Brandon (Camp near Fredericksburg, Virginia) to ‘Folks at Home’ - December 7, 1862.” Letters (correspondence). Civil War Collection, 1862. Box 1, Folder 34. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/699n2z35wg-cor.