MLA
McKee, W. J. Letter from W. J. McKee (Helena, Arkansas) to Columbus Peed, Informing Him of a Miniture Portrait [of Elizabeth Peed] and How He Came upon the Picture. McKee Was a Captain in the 33rd Missouri Infantry Regiment - May 20, 1863 (Typescript). 1863. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 20, Folder 8. https://digital.library.emory.edu/purl/061djh9x5m-cor.
APA, 6th edition
McKee, W. J. (1863). Letter from W. J. McKee (Helena, Arkansas) to Columbus Peed, informing him of a miniture portrait [of Elizabeth Peed] and how he came upon the picture. McKee was a captain in the 33rd Missouri Infantry Regiment - May 20, 1863 (typescript) (Box 20, Folder 8) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/061djh9x5m-cor.
Chicago
McKee, W. J. “Letter from W. J. McKee (Helena, Arkansas) to Columbus Peed, Informing Him of a Miniture Portrait [of Elizabeth Peed] and How He Came upon the Picture. McKee Was a Captain in the 33rd Missouri Infantry Regiment - May 20, 1863 (Typescript).” Letters (correspondence). Civil War Collection, 1863. Box 20, Folder 8. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/061djh9x5m-cor.