MLA
Blair, Robert F. Letter from Robert F. Blair, (Camp Curtin, Harrisburg, Pennsylvania) to "Dear Wife," Regarding Conditions at a Union Army Training Camp - December 22, 1861 (Typescript). 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 19, Folder 6. https://digital.library.emory.edu/purl/419s1rn9tc-cor.
APA, 6th edition
Blair, R. F. (1861). Letter from Robert F. Blair, (Camp Curtin, Harrisburg, Pennsylvania) to "Dear Wife," regarding conditions at a Union Army training camp - December 22, 1861 (typescript) (Box 19, Folder 6) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/419s1rn9tc-cor.
Chicago
Blair, Robert F. “Letter from Robert F. Blair, (Camp Curtin, Harrisburg, Pennsylvania) to ‘Dear Wife," Regarding Conditions at a Union Army Training Camp - December 22, 1861 (Typescript).” Letters (correspondence). Civil War Collection, 1861. Box 19, Folder 6. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/419s1rn9tc-cor.