MLA
Sheddon, Hugh. Letter from Hugh Sheddon (Liverpool, England) to James Seddon (Richmond, Virginia), Confederate States Secretary of War, with a New Flag to Replace the Flag That Has Been Permanently Hoisted over the Grave of Confederate General Thomas "Stonewall" Jackson - January 25, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 10, Folder 4. https://digital.library.emory.edu/purl/651vdnckw4-cor.
APA, 6th edition
Sheddon, H. (1864). Letter from Hugh Sheddon (Liverpool, England) to James Seddon (Richmond, Virginia), Confederate States Secretary of War, with a new flag to replace the flag that has been permanently hoisted over the grave of Confederate general Thomas "Stonewall" Jackson - January 25, 1864 (Box 10, Folder 4) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/651vdnckw4-cor.
Chicago
Sheddon, Hugh. “Letter from Hugh Sheddon (Liverpool, England) to James Seddon (Richmond, Virginia), Confederate States Secretary of War, with a New Flag to Replace the Flag That Has Been Permanently Hoisted over the Grave of Confederate General Thomas ‘Stonewall’ Jackson - January 25, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 10, Folder 4. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/651vdnckw4-cor.