Sources: PBL
- Samuel L. Clemens to Edward P. Hingston, 15 January 1867 · New York, N.Y · UCCL00118 PBL
- Samuel L. Clemens to Frank Fuller, 2 December 1867 · Washington, D.C · UCCL00167 PBL
- Samuel L. Clemens to Orion Clemens, 9 March 1871 · Buffalo, N.Y · UCCL00584 PBL
- Samuel L. Clemens to Joseph H. and Harmony C. Twichell, 19–22 March 1872 · Elmira, N.Y · UCCL00735 PBL
- Samuel L. Clemens to Charles Dudley Warner, 13 May 1873 · Elmira, N. Y · UCCL00915 PBL
- Samuel L. Clemens to Unidentified, August 1877 · Unknown place · UCCL09283 PBL
- SLC to Edmund Clarence Stedman, 10 January 1883 · Hartford, Conn · UCCL02333 PBL
- SLC to Edmund Clarence Stedman, 6 February 1883 · Hartford, Conn · UCCL02344 PBL
- SLC to Miss Mary ?, 31 May 1889 · Hartford, Conn · UCCL03898 PBL
- SLC to William H. Rideing, 19 February 1894 · New York, N.Y · UCCL04681 PBL
- SLC to Thomas S. Frisbie, 25 October 1897 · Vienna, Austria · UCCL05302 PBL
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