Sources: CCC
- John T. Metcalf to SLC, 19 September 1870 · Lansing, Iowa · UCLC31687 CCC
- Samuel L. Clemens to Elisha Bliss, Jr., 21? September 1870 · Buffalo, N.Y · UCCL00508 CCC
- SLC to James R. Osgood, 7 May 1881 · Hartford, Conn · UCCL01949 CCC
- SLC to Josiah G. Holland, 5 September 1881 · Elmira, N.Y · UCCL02028 CCC
- SLC to Karl Gerhardt, 24 September 1884 · Elmira, N.Y · UCCL00297 CCC
- SLC to Charles W. Stoddard, 16 March 1886 · Hartford, Conn · UCCL03376 CCC
- SLC to Unidentified, 29 December 1888 · Hartford, Conn · UCCL13254 CCC
- SLC to Mr. Goodwin, 8 November 1889 · Hartford, Conn · UCCL03961 CCC
- SLC to Francis E. Bliss, 30 May 1895 · Elmira, N.Y · UCCL04881 CCC
- SLC to William Carey, 14 June 1897 · London, England · UCCL05226 CCC
- SLC to William Winter, 7 July 1905 · Dublin, N.H · UCCL07078 CCC
- Samuel L. Clemens to D.E. Blake, Unknown date · Unknown place · UCCL00314 CCC
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