Sources: PHi
- Samuel L. Clemens to T. B. Pugh, 23 September 1872 · London, England · UCCL00812 PHi
- Samuel L. Clemens to T. B. Pugh, 20 January 1873 · Hartford, Conn · UCCL00860 PHi
- Samuel L. Clemens to Unidentified, 23 March 1874 · Hartford, Conn · UCCL01067 PHi
- Samuel L. Clemens to R. Shelton Mackenzie, 23 September 1874 · Hartford, Conn · UCCL01130 PHi
- Samuel L. Clemens to Simon Gratz, 16 December 1874? · Hartford, Conn · UCCL00845 PHi
- Samuel L. Clemens to Frank M. Etting, 23 February 1876 · Hartford, Conn · UCCL01309 PHi
- SLC to A. V. S. Anthony, 3 June 1881 · Hartford, Conn · UCCL01967 PHi
- SLC to Pennsylvania Historical Society, 8 December 1885 · Hartford, Conn · UCCL03327 PHi
- SLC to Wayne MacVeagh, 27 September 1896 · London, England · UCCL05118 PHi
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