MLA
Scott, John, 1820-1907. Letters to an officer in the army : proposing constitutional reform in the Confederate government after the close of the present war : a supplement to "The lost principle". 1864. Civil War Imprints. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/941zcrjhz2-cor.
APA, 6th edition
Scott, John, 1820-1907. (1864)[Letters to an officer in the army : proposing constitutional reform in the Confederate government after the close of the present war : a supplement to "The lost principle"]. Civil War Imprints, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/941zcrjhz2-cor.
Chicago
Scott, John, 1820-1907, Letters to an officer in the army : proposing constitutional reform in the Confederate government after the close of the present war : a supplement to "The lost principle", 1864, Civil War Imprints, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/941zcrjhz2-cor.