MLA
Kemper, James Lawson, 1823-1895. Note from James Lawson Kemper (Richmond, Virginia) to [?] Thorne, thanking him for the book - February 23, 1876. February 23, 1876. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/023vt4b9fp-cor.
APA, 6th edition
Kemper, James Lawson, 1823-1895. (February 23, 1876)[Note from James Lawson Kemper (Richmond, Virginia) to [?] Thorne, thanking him for the book - February 23, 1876]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/023vt4b9fp-cor.
Chicago
Kemper, James Lawson, 1823-1895, Note from James Lawson Kemper (Richmond, Virginia) to [?] Thorne, thanking him for the book - February 23, 1876, February 23, 1876, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/023vt4b9fp-cor.