Sources: NN5
- Samuel L. Clemens to Frank Fuller, 24 November 1867 · Washington, D.C · UCCL00158
- Samuel L. Clemens to Frank Fuller, 13 December 1867 · Washington, D.C · UCCL00173
- Samuel L. Clemens to Emily A Severance, 24 December 1867 · Washington, D.C · UCCL02780
- Samuel L. Clemens to Joseph H. Twichell, 3 January 1871 · Buffalo, N.Y · UCCL00554
- Samuel L. Clemens to Bret Harte, 7 June–28 September 1871 · Elmira, N.Y · UCCL11811
- Samuel L. Clemens to Samuel S. Cox, 4 February 1874 · Hartford, Conn · UCCL01046
- Samuel L. Clemens to Samuel S. Cox, 8 February 1875 · Hartford, Conn · UCCL01190
- Samuel L. Clemens to Dean Sage, 22 April 1875 · Hartford, Conn · UCCL01221
- Samuel L. Clemens to Thomas Bailey Aldrich, 28 January 1876 · Hartford, Conn · UCCL01303
- Samuel L. Clemens to Frank Fuller, 26 November 1879 · Hartford, Conn · UCCL01747
- SLC to Karl Gerhardt and Hattie J. Gerhardt, 4 August 1882 · Elmira, N.Y · UCCL02259
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