MLA
Thornton, Samuel S. Letter from Samuel S. Thornton (Camp Buckner, Talladega, Alabama) to "Miss Eliza J. Burnett" - June 8, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 52. https://digital.library.emory.edu/purl/477sn02vvh-cor.
APA, 6th edition
Thornton, S. S. (1864). Letter from Samuel S. Thornton (Camp Buckner, Talladega, Alabama) to "Miss Eliza J. Burnett" - June 8, 1864 (Box 6, Folder 52) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/477sn02vvh-cor.
Chicago
Thornton, Samuel S. “Letter from Samuel S. Thornton (Camp Buckner, Talladega, Alabama) to ‘Miss Eliza J. Burnett’ - June 8, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 6, Folder 52. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/477sn02vvh-cor.