MLA
Unintelligible Letter. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 3, Folder 3. https://digital.library.emory.edu/purl/197xksn14f-cor.
APA, 6th edition
Unintelligible letter (Box 3, Folder 3). [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/197xksn14f-cor.
Chicago
“Unintelligible Letter.” Letters (correspondence). Civil War Collection, n.d. Box 3, Folder 3. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/197xksn14f-cor.