MLA
Shuler, Alfred. Letter from Alfred Shuler (Camp Desassure, Summerville, South Carolina) to "My Dear Wife". Alfred Shuler Served in Company D of the 18th South Carolina Infantry Regiment - January 18, 1865. 1865. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 21. https://digital.library.emory.edu/purl/477sn02vvg-cor.
APA, 6th edition
Shuler, A. (1865). Letter from Alfred Shuler (Camp Desassure, Summerville, South Carolina) to "My Dear Wife". Alfred Shuler served in Company D of the 18th South Carolina Infantry Regiment - January 18, 1865 (Box 6, Folder 21) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/477sn02vvg-cor.
Chicago
Shuler, Alfred. “Letter from Alfred Shuler (Camp Desassure, Summerville, South Carolina) to ‘My Dear Wife’. Alfred Shuler Served in Company D of the 18th South Carolina Infantry Regiment - January 18, 1865.” Letters (correspondence). Civil War Collection, 1865. Box 6, Folder 21. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/477sn02vvg-cor.