Sources: NBuHi
- Samuel L. Clemens to Elisha Bliss, Jr., 14 August 1869 · Buffalo, N.Y · UCCL00331
- Samuel L. Clemens to Josephus N. Larned, 22 March 1873 · Hartford, Conn · UCCL00889
- Samuel L. Clemens to Joseph J. Albright, 17 July 1874 · Elmira, N. Y · UCCL01112
- SLC to George W. Benson, February–March 1883 · Hartford, Conn · UCCL11644
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