Sources: NvU
- SLC to Unidentified, December 1869 · Unknown place · UCCL10674 NvU
- James Redpath to SLC, 24 April 1872 · Boston, Mass. · UCLC50218 NvU
- Samuel L. Clemens to Francis E. Bliss, 25 April 1872 · Elmira, N.Y · UCCL09424 NvU
- SLC to OLC, December 1874 · Hartford, Conn · UCCL09710 NvU
- Henry Lee to SLC, 13 August 1879 · UCLC37339 NvU
- SLC to Moncure D. Conway, 5 February 1882 · Hartford, Conn · UCCL02157 NvU
- SLC to Frederick J. Hall, 21 December 1890 · Hartford, Conn · UCCL04003 NvU
- SLC to Unidentified, 24 April 1900 · London, England · UCCL05798 NvU
- SLC to Unidentified, 9 October 1902 · York Harbor, Me · UCCL08867 NvU
- William Culver "Bobs" Roberts to SLC, Unknown date · UCLC37338 NvU
- Isaac H. Platt to SLC, May 1909 · Wallingford, Pa. · UCLC37346 NvU
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