Sources: OKeU
- Samuel L. Clemens to Cornelius R. Agnew, 7 June 1875 · Hartford, Conn · UCCL01238
- Samuel L. Clemens to Cornelius R. Agnew, 23 June 1875 · Hartford, Conn · UCCL01243
- Samuel L. Clemens to Cornelius R. Agnew, 30 June 1875 · Hartford, Conn · UCCL01245
- OLC to Cornelius R. Agnew, 26 November 1875 · Hartford, Conn · UCCL01284
- SLC to Ulysses S. Grant, 15 March 1881 · Hartford, Conn · UCCL01927
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