Sources: Mn2
- Samuel L. Clemens to Emeline B. Beach, 10 February 1868 · Washington, D.C · UCCL00192
- Samuel L. Clemens to Josiah G. Holland, 29 April 1875 · Hartford, Conn · UCCL01266
- SLC to Clara L. Clemens, 19 December 1892 · Florence, Italy · UCCL04310
- SLC to Clara L. Clemens, 9 January 1893 · Florence, Italy · UCCL04324
- SLC to Frederick J. Hall, 24 October 1893 · New York, N.Y · UCCL08983
- SLC to Judge Markham, 26 February 1896 · Cawnpore, India · UCCL11410
- SLC to Unidentified, October 1897 · Vienna, Austria · UCCL11436
- SLC to Virginia F. Boyle, 6 January 1902 · Riverdale, N.Y · UCCL06221
- SLC to Sophie Sloan, 30 May–9 June 1902 · Clayton, Mo · UCCL12647
- SLC to Unidentified, 16 January 1903 · Riverdale, N.Y · UCCL06566
- SLC to Clara L. Clemens, 4 September 1904 · New York, N.Y · UCCL11434
- SLC to Clara L. Clemens, 18–19 June 1906 · Dublin, N.H · UCCL07462
- SLC to Barbara Mullen, 1 January 1907 · New York, N.Y · UCCL11543
- SLC to Kate D. Riggs, 17 January 1908 · New York, N.Y · UCCL11615
- SLC per Albert Bigelow Paine to Mary E. Moffett, 26 December–8 January 1910 · Redding, Conn · UCCL11535
- SLC per Albert Bigelow Paine to Virginia F. Boyle, 26 December–10 January 1910 · Redding, Conn · UCCL11542
- SLC to Unidentified, Unknown date · Unknown place · UCCL12648
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