Sources: PPiU
- Samuel L. Clemens to Elisha Bliss, Jr., 23 June 1868 · San Francisco, Calif · UCCL02736
- Samuel L. Clemens to Elisha Bliss, Jr., 14 February 1869 · Ravenna, Ohio, · UCCL00251
- SLC to Joseph H. Twichell, 16? March 1897 · London, England · UCCL14146
- SLC to L. M. Powers, 19 February 1902 · Riverdale, N.Y · UCCL06281
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