MLA
Tucker, John Randolph. Letter from John Randolph Tucker (Richmond, Virginia) to H. A. Crane; Regarding His Brother Alfred Tucker's Death - October 8, 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 56. https://digital.library.emory.edu/purl/740ksn03k5-cor.
APA, 6th edition
Tucker, J. R. (1862). Letter from John Randolph Tucker (Richmond, Virginia) to H. A. Crane; regarding his brother Alfred Tucker's death - October 8, 1862 (Box 6, Folder 56) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/740ksn03k5-cor.
Chicago
Tucker, John Randolph. “Letter from John Randolph Tucker (Richmond, Virginia) to H. A. Crane; Regarding His Brother Alfred Tucker's Death - October 8, 1862.” Letters (correspondence). Civil War Collection, 1862. Box 6, Folder 56. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/740ksn03k5-cor.