MLA
Smith, J. Soule. Letter from J. Soule Smith to G. H. Thompson - August 6, 1889 (Photocopy). 1889. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 3, Folder 49. https://digital.library.emory.edu/purl/3418kprs4m-cor.
APA, 6th edition
Smith, J. S. (1889). Letter from J. Soule Smith to G. H. Thompson - August 6, 1889 (photocopy) (Box 3, Folder 49) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/3418kprs4m-cor.
Chicago
Smith, J. Soule. “Letter from J. Soule Smith to G. H. Thompson - August 6, 1889 (Photocopy).” Letters (correspondence). Civil War Collection, 1889. Box 3, Folder 49. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/3418kprs4m-cor.