MLA
Sullivan, George Washington. Letter from George Washington Sullivan (Columbia, South Carolina) to His Wife - November 30, 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 39. https://digital.library.emory.edu/purl/682k6djj1s-cor.
APA, 6th edition
Sullivan, G. W. (1862). Letter from George Washington Sullivan (Columbia, South Carolina) to his wife - November 30, 1862 (Box 6, Folder 39) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/682k6djj1s-cor.
Chicago
Sullivan, George Washington. “Letter from George Washington Sullivan (Columbia, South Carolina) to His Wife - November 30, 1862.” Letters (correspondence). Civil War Collection, 1862. Box 6, Folder 39. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/682k6djj1s-cor.