MLA
Blake, G. M. Letter from G. M. Blake (John's Island, [S.C.]) to "Dear Mother." G. M. Blake Served with the 6th South Carolina Cavalry Regiment, Also Known as Aiken's Rangers or Dixie Rangers and Later Served in the Signal Corps - November 13, 1863. 1863. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 31. https://digital.library.emory.edu/purl/494vhhmhr5-cor.
APA, 6th edition
Blake, G. M. (1863). Letter from G. M. Blake (John's Island, [S.C.]) to "Dear Mother." G. M. Blake served with the 6th South Carolina Cavalry Regiment, also known as Aiken's Rangers or Dixie Rangers and later served in the Signal Corps - November 13, 1863 (Box 1, Folder 31) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/494vhhmhr5-cor.
Chicago
Blake, G. M. “Letter from G. M. Blake (John's Island, [S.C.]) to ‘Dear Mother." G. M. Blake Served with the 6th South Carolina Cavalry Regiment, Also Known as Aiken's Rangers or Dixie Rangers and Later Served in the Signal Corps - November 13, 1863.” Letters (correspondence). Civil War Collection, 1863. Box 1, Folder 31. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/494vhhmhr5-cor.