MLA
Rowe, Belle A. Letter from Belle A. Rowe to "Dear Brother" - October 23, 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 19, Folder 12. https://digital.library.emory.edu/purl/170msbcd48-cor.
APA, 6th edition
Rowe, B. A. (1862). Letter from Belle A. Rowe to "Dear Brother" - October 23, 1862 (Box 19, Folder 12) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/170msbcd48-cor.
Chicago
Rowe, Belle A. “Letter from Belle A. Rowe to ‘Dear Brother’ - October 23, 1862.” Letters (correspondence). Civil War Collection, 1862. Box 19, Folder 12. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/170msbcd48-cor.