MLA
Cabe, J. D. Letter from J. D. Cabe (Camp Clingman) to "Miss C. C. C." - September 7, 1861. 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 2, Folder 1. https://digital.library.emory.edu/purl/3074tmph50-cor.
APA, 6th edition
Cabe, J. D. (1861). Letter from J. D. Cabe (Camp Clingman) to "Miss C. C. C." - September 7, 1861 (Box 2, Folder 1) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/3074tmph50-cor.
Chicago
Cabe, J. D. “Letter from J. D. Cabe (Camp Clingman) to ‘Miss C. C. C." - September 7, 1861.” Letters (correspondence). Civil War Collection, 1861. Box 2, Folder 1. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/3074tmph50-cor.