Sources: CSt
- Samuel L. Clemens to Jane L. Stanford, April 1870 · Buffalo, N.Y · UCCL11712 CSt
- SLC to Frank Fuller, 18 February 1894 · New York, N.Y · UCCL04694 CSt
- SLC to Rudyard Kipling, 23 May 1901 · New York, N.Y · UCCL06063 CSt
- SLC to Charles W. Stoddard, 15 December 1902 · Riverdale, N.Y · UCCL06520 CSt
- SLC to George B. Harvey, 5 September 1905 · Dublin, N.H · UCCL07129 CU-MARK, CSt
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