MLA
Spencer, Thomas. Letter from Thomas Spencer to “Mrs. Moody” Regarding Creating Grave Markers for Isaac P. Baker, John Major Baker and William S. Baker - May 21, 1962. 1962. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 8, Folder 4. https://digital.library.emory.edu/purl/945cc2frp5-cor.
APA, 6th edition
Spencer, T. (1962). Letter from Thomas Spencer to “Mrs. Moody” regarding creating grave markers for Isaac P. Baker, John Major Baker and William S. Baker - May 21, 1962 (Box 8, Folder 4) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/945cc2frp5-cor.
Chicago
Spencer, Thomas. “Letter from Thomas Spencer to ‘Mrs. Moody’ Regarding Creating Grave Markers for Isaac P. Baker, John Major Baker and William S. Baker - May 21, 1962.” Letters (correspondence). Civil War Collection, 1962. Box 8, Folder 4. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/945cc2frp5-cor.