MLA
Depot, New-York Union Envelope. Union Patriotic Envelopes Dealing with Secession - "Missouri Tasting Secession Soup, and Gets Burnt! and Thinks She Won't Go in." Published by New-York Union Envelope Depot. New-York Union Envelope Depot, 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 21, Folder 8. https://digital.library.emory.edu/purl/7547pvmf1g-cor.
APA, 6th edition
Depot, N.-Y. U. E. (1861). Union patriotic envelopes dealing with secession - "Missouri tasting Secession Soup, and gets Burnt! and thinks she won't go in." Published by New-York Union Envelope Depot (Box 21, Folder 8) [Envelopes]. New-York Union Envelope Depot; Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/7547pvmf1g-cor.
Chicago
Depot, New-York Union Envelope. “Union Patriotic Envelopes Dealing with Secession - ‘Missouri Tasting Secession Soup, and Gets Burnt! and Thinks She Won't Go in." Published by New-York Union Envelope Depot.” Envelopes. Civil War Collection. New York City, NY: New-York Union Envelope Depot, 1861. Box 21, Folder 8. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/7547pvmf1g-cor.