Sources: NIC
- Samuel L. Clemens to Bayard Taylor, 24 January 1877 · Hartford, Conn · UCCL01403 CtY-BR, NIC
- Samuel L. Clemens to Bayard Taylor, 28 February 1878 · Hartford, Conn · UCCL01538 NIC
- Samuel L. Clemens to Bayard Taylor, 7 May 1878 · Heidelberg, Germany · UCCL01560 NIC
- Samuel L. Clemens to Bayard Taylor, 10 June 1878 · Heidelberg, Germany · UCCL01570 NIC
- Samuel L. Clemens to Bayard Taylor, 8 September 1878 · Geneva, Switzerland · UCCL01594 NIC
- Samuel L. Clemens to Bayard Taylor, 14 December 1878 · Munich, Germany · UCCL01614 NIC
- Joel Chandler Harris to SLC, 6 December 1881 · Atlanta, Ga. · UCLC40938 NIC
- SLC to \"Jack,\" 23 June 1882 · Hartford, Conn · UCCL02225 NN4, NIC
- SLC to Julius John William Krueger, 22 July 1883 · Elmira, N.Y · UCCL01749 NIC
- SLC to Frederick J. Hall, 5 October 1885 · Hartford, Conn · UCCL03292 NIC
- SLC to Daniel Willard Fiske, 8? May 1892 · Florence, Italy · UCCL13444 NIC
- SLC to Willard Fiske, 29 May 1892 · Cadenabbia, Italy · UCCL11369 NIC
- SLC to Willard Fiske, 12 June 1892 · Bad Nauheim, Germany · UCCL11370 NIC
- SLC to Willard Fiske, 5 November 1892 · Florence, Italy · UCCL11371 NIC
- SLC to Willard Fiske, 2 February 1893 · Florence, Italy · UCCL11372 NIC
- SLC to OLC, 28–31 October 1893 · Hartford, Conn · UCCL12386 NIC
- SLC to Willard Fiske, 15 July 1899 · Sanna, Sweden · UCCL11373 NIC
- SLC to Willard Fiske, 26 July 1900 · London, England · UCCL11382 NIC
- SLC to Willard Fiske, 25 September 1900 · London, England · UCCL11383 NIC
- SLC to Willard Fiske, 25 September–6 October 1900 · London, England · UCCL11384 NIC
- SLC to Willard Fiske, 1 June 1903 · Unknown place · UCCL11381 NIC
- SLC to Willard Fiske, 1 June 1903 · New York, N.Y · UCCL11375 NIC
- SLC to Willard Fiske, 14 July 1903 · Elmira, N.Y · UCCL11376 NIC
- SLC to Willard Fiske, 19 July 1903 · Elmira, N.Y · UCCL11377 NIC
- SLC to Willard Fiske, 10 November 1903 · Florence, Italy · UCCL11378 NIC
- SLC to Willard Fiske, 14 November 1903 · Florence, Italy · UCCL11379 NIC
- SLC to Willard Fiske, 24 November 1903 · Florence, Italy · UCCL11380 NIC
- SLC per Isabel V. Lyon to Willard Fiske, 18 January 1904 · Florence, Italy · UCCL11374 NIC
- SLC to Michael Monahan, 4 February 1905 · New York, N.Y · UCCL06992 NIC
- SLC to Clara L. Clemens, 5 March 1907 · New York, N.Y · UCCL07671 InFw2, NIC
- SLC to William D. Howells, 17 September n.y. · Unknown place · UCCL10183 NIC
- SLC to S. J. Medill, 2 October n.y. · Unknown place · UCCL04482 NIC
- SLC to John S. Hart, Unknown date, Hartford, Conn · UCCL05522 NIC
1