Sources: ICN
- Samuel L. Clemens to Moncure D. Conway, 4 July 1873 · London, England · UCCL00943 ICN
- Samuel L. Clemens to Albert J. Scott, 27 October 1879 · Hartford, Conn · UCCL01701 ICN
- Samuel L. Clemens to Melville E. Stone, 3 April 1880 · Hartford, Conn · UCCL01781 ICN
- SLC to Melville E. Stone, 11 September 1904 · New York, N.Y · UCCL06921 ICN
- SLC, Clara L. Clemens to Melville E. Stone, 8 February 1908 · New York, N.Y · UCCL07931 ICN
- SLC to Melville E. Stone, 30 September 1909 · Redding, Conn · UCCL08461 ICN
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