MLA
Warthen, George W. Letter from George W. Warthen (Camp at Baldwin, Florida) to His Sister. George Served in the 28th Georgia Infantry Regiment - April 15, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 7, Folder 13. https://digital.library.emory.edu/purl/204rjdfp3t-cor.
APA, 6th edition
Warthen, G. W. (1864). Letter from George W. Warthen (Camp at Baldwin, Florida) to his sister. George served in the 28th Georgia Infantry Regiment - April 15, 1864 (Box 7, Folder 13) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/204rjdfp3t-cor.
Chicago
Warthen, George W. “Letter from George W. Warthen (Camp at Baldwin, Florida) to His Sister. George Served in the 28th Georgia Infantry Regiment - April 15, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 7, Folder 13. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/204rjdfp3t-cor.