MLA
Wells, John G. (John Gaylord), 1821-1880. Union patriotic envelope with George B. McClellan cartoon - "Maj. Gen. McClellan, Commander of the Federal Forces on the Potomac". 1861~. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/0515mkkxkw-cor.
APA, 6th edition
Wells, John G. (John Gaylord), 1821-1880. (1861~)[Union patriotic envelope with George B. McClellan cartoon - "Maj. Gen. McClellan, Commander of the Federal Forces on the Potomac"]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/0515mkkxkw-cor.
Chicago
Wells, John G. (John Gaylord), 1821-1880, Union patriotic envelope with George B. McClellan cartoon - "Maj. Gen. McClellan, Commander of the Federal Forces on the Potomac", 1861~, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/0515mkkxkw-cor.