MLA
Andrews, William P. Letter from William P. Andrews (Dalton, Georgia) to "Dear Friend" - August 2, 1863. 1863. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 7. https://digital.library.emory.edu/purl/344pk0p3nd-cor.
APA, 6th edition
Andrews, W. P. (1863). Letter from William P. Andrews (Dalton, Georgia) to "Dear Friend" - August 2, 1863 (Box 1, Folder 7) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/344pk0p3nd-cor.
Chicago
Andrews, William P. “Letter from William P. Andrews (Dalton, Georgia) to ‘Dear Friend’ - August 2, 1863.” Letters (correspondence). Civil War Collection, 1863. Box 1, Folder 7. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/344pk0p3nd-cor.