MLA
Stiles, Joseph Clay. Letter from Joseph Clay Stiles (Richmond, Virginia) to His Wife, Sarah, Regarding Religious Conversion of Soldiers - 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 35. https://digital.library.emory.edu/purl/7547pvmdk6-cor.
APA, 6th edition
Stiles, J. C. (1862). Letter from Joseph Clay Stiles (Richmond, Virginia) to his wife, Sarah, regarding religious conversion of soldiers - 1862 (Box 6, Folder 35) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/7547pvmdk6-cor.
Chicago
Stiles, Joseph Clay. “Letter from Joseph Clay Stiles (Richmond, Virginia) to His Wife, Sarah, Regarding Religious Conversion of Soldiers - 1862.” Letters (correspondence). Civil War Collection, 1862. Box 6, Folder 35. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/7547pvmdk6-cor.