MLA
Clay, C. C. (Clement Claiborne), 1816-1882. Signature of Alabama Senator Clement Claiborne Clay Jr.. unknown. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/897kprr5wz-cor.
APA, 6th edition
Clay, C. C. (Clement Claiborne), 1816-1882. (unknown)[Signature of Alabama Senator Clement Claiborne Clay Jr.]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/897kprr5wz-cor.
Chicago
Clay, C. C. (Clement Claiborne), 1816-1882, Signature of Alabama Senator Clement Claiborne Clay Jr., unknown, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/897kprr5wz-cor.