MLA
Tyler, John, Jr. Letter from John Jr. Tyler (near Ellison's Mills, Hanover County, Virginia) to [?] Roane, Detailing the Battle of Cold Harbor - June 4, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 59. https://digital.library.emory.edu/purl/713905qgk1-cor.
APA, 6th edition
Tyler, J., Jr. (1864). Letter from John Jr. Tyler (near Ellison's Mills, Hanover County, Virginia) to [?] Roane, detailing the Battle of Cold Harbor - June 4, 1864 (Box 6, Folder 59) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/713905qgk1-cor.
Chicago
Tyler, John, Jr. “Letter from John Jr. Tyler (near Ellison's Mills, Hanover County, Virginia) to [?] Roane, Detailing the Battle of Cold Harbor - June 4, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 6, Folder 59. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/713905qgk1-cor.