MLA
Speir, James H. Letter from James H. Speir to [Unknown]. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 53. https://digital.library.emory.edu/purl/535t76hfg2-cor.
APA, 6th edition
Speir, J. H. Letter from James H. Speir to [unknown] (Box 6, Folder 53) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/535t76hfg2-cor.
Chicago
Speir, James H. “Letter from James H. Speir to [Unknown].” Letters (correspondence). Civil War Collection, n.d. Box 6, Folder 53. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/535t76hfg2-cor.