MLA
Rush, John Wesley. Letter from John Wesley Rush (Camp Chase, Columbus, Ohio) to His Father as a Prisoner of War. Wesley, a Methodist Minister and Editor of the Alabama Christian Advocate Served in the Confederate Army as a Captain in an Alabama Regiment, and Possibly as a Chaplain - April 19, 1862 (Typescript). 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 7. https://digital.library.emory.edu/purl/85370rxx4q-cor.
APA, 6th edition
Rush, J. W. (1862). Letter from John Wesley Rush (Camp Chase, Columbus, Ohio) to his father as a prisoner of war. Wesley, a Methodist minister and editor of the Alabama Christian Advocate served in the Confederate Army as a captain in an Alabama regiment, and possibly as a chaplain - April 19, 1862 (typescript) (Box 6, Folder 7) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/85370rxx4q-cor.
Chicago
Rush, John Wesley. “Letter from John Wesley Rush (Camp Chase, Columbus, Ohio) to His Father as a Prisoner of War. Wesley, a Methodist Minister and Editor of the Alabama Christian Advocate Served in the Confederate Army as a Captain in an Alabama Regiment, and Possibly as a Chaplain - April 19, 1862 (Typescript).” Letters (correspondence). Civil War Collection, 1862. Box 6, Folder 7. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/85370rxx4q-cor.