MLA
Davis, Samuel. Letter from Samuel Davis (Portsmouth, Virginia) to John Oliver - March 27, 1863. 1863. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 3, Folder, 1. https://digital.library.emory.edu/purl/2322bvq93c-cor.
APA, 6th edition
Davis, S. (1863). Letter from Samuel Davis (Portsmouth, Virginia) to John Oliver - March 27, 1863 (Box 3, Folder, 1) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/2322bvq93c-cor.
Chicago
Davis, Samuel. “Letter from Samuel Davis (Portsmouth, Virginia) to John Oliver - March 27, 1863.” Letters (correspondence). Civil War Collection, 1863. Box 3, Folder, 1. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/2322bvq93c-cor.