MLA
Wilkins, B. G. Letter from B. G. Wilkins to David Flavel Jamison about Presenting a Company Flag - February 13, 1861. 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 4, Folder 7. https://digital.library.emory.edu/purl/723hx3fgc4-cor.
APA, 6th edition
Wilkins, B. G. (1861). Letter from B. G. Wilkins to David Flavel Jamison about presenting a company flag - February 13, 1861 (Box 4, Folder 7) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/723hx3fgc4-cor.
Chicago
Wilkins, B. G. “ Letter from B. G. Wilkins to David Flavel Jamison about Presenting a Company Flag - February 13, 1861.” Letters (correspondence). Civil War Collection, 1861. Box 4, Folder 7. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/723hx3fgc4-cor.