MLA
Envelope with Confederate Generals on Them - "[Louis] Wigfall on His Promised Descent on Washington". 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 21, Folder 5. https://digital.library.emory.edu/purl/501pg4f5xh-cor.
APA, 6th edition
Envelope with Confederate generals on them - "[Louis] Wigfall on his promised descent on Washington" (Box 21, Folder 5). (1861). [Envelopes]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/501pg4f5xh-cor.
Chicago
“Envelope with Confederate Generals on Them - "[Louis] Wigfall on His Promised Descent on Washington.’” Envelopes. Civil War Collection, 1861. Box 21, Folder 5. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/501pg4f5xh-cor.