Sources: MB
- Samuel L. Clemens to Elisha Bliss, Jr., 13 October 1870 · Buffalo, N.Y · UCCL00511
- Samuel L. Clemens to James Redpath, 15 May 1872 · Elmira, N.Y · UCCL00748
- Samuel L. Clemens to Kate Field, 9 June 1873 · London, England · UCCL00920
- Samuel L. Clemens to Chatto and Windus, 8 April 1874 · Hartford, Conn · UCCL01072
- Samuel L. Clemens to Charles Warren Stoddard, 1 February 1875 · Hartford, Conn · UCCL01187
- Samuel L. Clemens to Charles Warren Stoddard, 20 March 1878 · Hartford, Conn · UCCL01546
- SLC to Karl Gerhardt and Hattie J. Gerhardt, 9 May 1881 · Hartford, Conn · UCCL01952
- SLC to Karl Gerhardt, 30 May 1881 · Hartford, Conn · UCCL10064
- SLC to Karl and Hattie J. Gerhardt, 31 July 1881 · Branford, Conn · UCCL01991
- SLC to Karl Gerhardt and Hattie J. Gerhardt, 31 August 1881 · Elmira, N.Y · UCCL02019
- SLC to Karl Gerhardt and Hattie J. Gerhardt, 9 October 1881 · Hartford, Conn · UCCL02049
- SLC to Karl and Hattie J. Gerhardt, 7 November 1881 · Hartford, Conn · UCCL02083
- SLC to Karl Gerhardt and Hattie J. Gerhardt, 4 August 1882 · Elmira, N.Y · UCCL02259
- SLC to Karl Gerhardt, 30 September–1 October 1882 · Hartford, Conn · UCCL02282
- SLC to Karl Gerhardt and Hattie J. Gerhardt, 2 July 1883 · Elmira, N.Y · UCCL02300
- SLC to George Parsons Lathrop, 14 April 1884 · Hartford, Conn · UCCL02952
- SLC to Karl Gerhardt, 28 September 1884 · Hartford, Conn · UCCL01443
- SLC to Karl Gerhardt, 10 April 1885 · Philadelphia, Pa · UCCL03211
- SLC to Karl Gerhardt, 26 June 1885 · Elmira, N.Y · UCCL03246
- SLC to Karl Gerhardt, 5 September 1885 · Elmira, N.Y · UCCL11710
- SLC, OLC to Karl Gerhardt, 22–23 February 1886 · Hartford, Conn · UCCL03370
- SLC to Karl Gerhardt, 15 July 1886 · Elmira, N.Y · UCCL03420
- SLC to Sylvester Baxter, 28 May 1887 · Hartford, Conn · UCCL03577
- SLC to Karl Gerhardt, 16 October 1889 · Hartford, Conn · UCCL03952
- SLC to Chatto & Windus, 12 June 1893 · Florence, Italy · UCCL04415
- SLC to Frank Fuller, 6 July 1895 · Elmira, N.Y · UCCL04927
- SLC to Robert Lutz, 27 February 1899 · Vienna, Austria · UCCL05551
- SLC to Robert Lutz, 3 April 1899 · Vienna, Austria · UCCL05574
- SLC to Robert Lutz, 14 July 1899 · Sanna, Sweden · UCCL05655
- SLC to Helen M. Winslow, 3 December 1900 · New York, N.Y · UCCL05926
- SLC to Mary E. Phillips, 14 February 1901 · New York, N.Y · UCCL05996
- SLC to Mary E. Phillips, 16 February 1901 · New York, N.Y · UCCL06002
- SLC to Mary E. Phillips, 14 April 1901 · New York, N.Y · UCCL06036
- SLC to Helen M. Winslow, 4 December 1901 · Riverdale, N.Y · UCCL06183
- SLC to Mary E. Phillips, 8 August 1904 · Lee, Mass · UCCL06911
- SLC to George B. Harvey, 22 February 1910 · Hamilton, Bermuda · UCCL08563
- SLC to Andrew Chatto, 1900 · Unknown place · UCCL05738
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