MLA
Lee, Robert E. (Robert Edward), 1807-1870. Letter from Confederate General Robert E. Lee to Confederate General James Longstreet - January 16, 1864 (typescript). January 16, 1864. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/044bnzs8jv-cor.
APA, 6th edition
Lee, Robert E. (Robert Edward), 1807-1870. (January 16, 1864)[Letter from Confederate General Robert E. Lee to Confederate General James Longstreet - January 16, 1864 (typescript)]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/044bnzs8jv-cor.
Chicago
Lee, Robert E. (Robert Edward), 1807-1870, Letter from Confederate General Robert E. Lee to Confederate General James Longstreet - January 16, 1864 (typescript), January 16, 1864, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/044bnzs8jv-cor.