MLA
Barnett, J. T. Letter from J. T. Barnett. (Camp Bucker, Talladega, Alabama) to "Dear Mother" - May 26, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 21. https://digital.library.emory.edu/purl/699n2z35wf-cor.
APA, 6th edition
Barnett, J. T. (1864). Letter from J. T. Barnett. (Camp Bucker, Talladega, Alabama) to "Dear mother" - May 26, 1864 (Box 1, Folder 21) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/699n2z35wf-cor.
Chicago
Barnett, J. T. “Letter from J. T. Barnett. (Camp Bucker, Talladega, Alabama) to ‘Dear Mother’ - May 26, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 1, Folder 21. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/699n2z35wf-cor.