MLA
Burden, W. W. Letter from W. W. Burden to His Sister, Elizabeth Burden - February 23, 1863 (Typescript). 1863. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 3, Folder 44. https://digital.library.emory.edu/purl/10966t1h32-cor.
APA, 6th edition
Burden, W. W. (1863). Letter from W. W. Burden to his sister, Elizabeth Burden - February 23, 1863 (typescript) (Box 3, Folder 44) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/10966t1h32-cor.
Chicago
Burden, W. W. “Letter from W. W. Burden to His Sister, Elizabeth Burden - February 23, 1863 (Typescript).” Letters (correspondence). Civil War Collection, 1863. Box 3, Folder 44. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/10966t1h32-cor.