MLA
Blackford, William H. Unaddressed Circular (Inspector's Office, Richmond, Virginia). 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 30. https://digital.library.emory.edu/purl/883xsj3vzj-cor.
APA, 6th edition
Blackford, W. H. (1864). Unaddressed circular (Inspector's Office, Richmond, Virginia) (Box 1, Folder 30) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/883xsj3vzj-cor.
Chicago
Blackford, William H. “Unaddressed Circular (Inspector's Office, Richmond, Virginia).” Letters (correspondence). Civil War Collection, 1864. Box 1, Folder 30. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/883xsj3vzj-cor.