Sources: DFo
- Samuel L. Clemens to Charles E. Flower, 14 July 1873 · London, England · UCCL00952
- Samuel L. Clemens to Charles E. Flower, 27 October 1875 · Hartford, Conn · UCCL01276
- Samuel L. Clemens to Augustin Daly, per Telegraph Operator, 3 August 1877 · Elmira, N.Y · UCCL01462
- Samuel L. Clemens to Augustin Daly, 15 August 1877 · New York, N.Y · UCCL01471
- SLC per Unidentified to Chatto & Windus, 18 January 1882 · Hartford, Conn · UCCL11890
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