MLA
Envelope Containing Letter from Christ C. McKinney (Camp in Virginia) to His Wife, Mary (Petersburg, Tennessee). McKinney Served in the 8th Tennessee Infantry Regiment - October 1, 1861. 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 5, Folder 7. https://digital.library.emory.edu/purl/945cc2fs19-cor.
APA, 6th edition
Envelope containing letter from Christ C. McKinney (Camp in Virginia) to his wife, Mary (Petersburg, Tennessee). McKinney served in the 8th Tennessee Infantry Regiment - October 1, 1861 (Box 5, Folder 7). (1861). [Envelopes]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/945cc2fs19-cor.
Chicago
“Envelope Containing Letter from Christ C. McKinney (Camp in Virginia) to His Wife, Mary (Petersburg, Tennessee). McKinney Served in the 8th Tennessee Infantry Regiment - October 1, 1861.” Envelopes. Civil War Collection, 1861. Box 5, Folder 7. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/945cc2fs19-cor.