Sources: NhD
- Samuel L. Clemens to Adolph H. Sutro, per Telegraph Operator, 24 August 1871 · Hartford, Conn · UCCL03649
- Samuel L. Clemens to Adolph H. Sutro, per Telegraph Operator, 25 August 1871 · Hartford, Conn · UCCL02815
- SLC to James R. Osgood, 12 December 1881 · Hartford, Conn · UCCL02116
- SLC to Jeannette L. Gilder, 15 December 1885 · Hartford, Conn · UCCL03330
- SLC to Edmund C. Stedman, 15 November 1900 · New York, N.Y · UCCL05908
- SLC to Robert M. Curts, 22 July 1907 · SS Minnetonka · UCCL07788
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