MLA
Letter from an Unknown Soldier (Harrisonburg, Virginia) to "Dear Brother" - July 8th, 1861. 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 72. https://digital.library.emory.edu/purl/194hmgqp8j-cor.
APA, 6th edition
Letter from an unknown soldier (Harrisonburg, Virginia) to "Dear Brother" - July 8th, 1861 (Box 6, Folder 72). (1861). [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/194hmgqp8j-cor.
Chicago
“Letter from an Unknown Soldier (Harrisonburg, Virginia) to ‘Dear Brother’ - July 8th, 1861.” Letters (correspondence). Civil War Collection, 1861. Box 6, Folder 72. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/194hmgqp8j-cor.