MLA
Caldwell, H. A. Letter from H. A. Caldwell (Zebulon, Georgia) to His Uncle, Charles Y. Caldwell (Perry, Houston County, Georgia) - May 22, 1850 (Typescript). 1850. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 2, Folder 2. https://digital.library.emory.edu/purl/887brv16dz-cor.
APA, 6th edition
Caldwell, H. A. (1850). Letter from H. A. Caldwell (Zebulon, Georgia) to his uncle, Charles Y. Caldwell (Perry, Houston County, Georgia) - May 22, 1850 (typescript) (Box 2, Folder 2) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/887brv16dz-cor.
Chicago
Caldwell, H. A. “Letter from H. A. Caldwell (Zebulon, Georgia) to His Uncle, Charles Y. Caldwell (Perry, Houston County, Georgia) - May 22, 1850 (Typescript).” Letters (correspondence). Civil War Collection, 1850. Box 2, Folder 2. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/887brv16dz-cor.