Sources: CtY
- Samuel L. Clemens to President of the Scroll and Key Society, 18 November 1868 · Cleveland, Ohio · UCCL02764
- Samuel L. Clemens to James Redpath, 10 May 1869 · Hartford, Conn · UCCL00298
- Samuel L. Clemens to William D. Whitney, 16 January 1875 · Hartford, Conn · UCCL08610
- Samuel L. Clemens to Elisha Bliss, Jr., 16? July 1875 · Hartford, Conn · UCCL01252
- SLC to Benjamin H. Ticknor, 9 September 1881 · Elmira, N.Y · UCCL02032
- SLC to Unidentified, 19 September 1881 · Elmira, N.Y · UCCL02040
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