MLA
Tillinghast, Edwin L. Letter from Edwin L. Tillinghast (Manchester Hospital, Virginia) to His Sister, Cornelia E. Tillinghast (Gillisonville, South Carolina). Edwin Served in the 3rd South Carolina Cavalry - March 7, 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 55. https://digital.library.emory.edu/purl/692t4b8hhs-cor.
APA, 6th edition
Tillinghast, E. L. (1862). Letter from Edwin L. Tillinghast (Manchester Hospital, Virginia) to his sister, Cornelia E. Tillinghast (Gillisonville, South Carolina). Edwin served in the 3rd South Carolina Cavalry - March 7, 1862 (Box 6, Folder 55) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/692t4b8hhs-cor.
Chicago
Tillinghast, Edwin L. “Letter from Edwin L. Tillinghast (Manchester Hospital, Virginia) to His Sister, Cornelia E. Tillinghast (Gillisonville, South Carolina). Edwin Served in the 3rd South Carolina Cavalry - March 7, 1862.” Letters (correspondence). Civil War Collection, 1862. Box 6, Folder 55. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/692t4b8hhs-cor.