MLA
Thompson, James W. Letter of Recommendation for William H. Scott, Sr. from James W. Thompson, December 21, 1878. 1878. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 1. https://digital.library.emory.edu/purl/098z8w9hxx-cor.
APA, 6th edition
Thompson, J. W. (1878). Letter of recommendation for William H. Scott, Sr. from James W. Thompson, December 21, 1878 (Box 1, Folder 1) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/098z8w9hxx-cor.
Chicago
Thompson, James W. “Letter of Recommendation for William H. Scott, Sr. from James W. Thompson, December 21, 1878.” Letters (correspondence). William H. Scott Family Papers, 1848-1982, 1878. Box 1, Folder 1. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/098z8w9hxx-cor.