Sources: Me4
- SLC to Orion Clemens, 7 May 1863 · San Francisco, Calif · UCCL12990 Me4
- Clarence C. Buel for Century Magazine to SLC, 13 January 1886 · New York, N.Y. · UCLC42855 Me4
- SLC to Arthur Jenkins, 1 February 1887 · Hartford, Conn · UCCL12976 Me4
- Edward Bellamy to SLC, 15 March 1890 · Brooklyn, N.Y. · UCLC50422 Me4
- Frederick J. Hall to SLC, 27 February 1894 · New York, N.Y. · UCLC45990 Me4
- SLC to Percy Spalding, 8 July 1897 · London, England · UCCL12988 Me4
- Henry C. Robinson to SLC, 29 December 1897 · Hartford, Conn. · UCLC46177 Me4
- Richard Watson Gilder, Robert U. Johnson and Clarence Buel to SLC, 30 November 1900 · UCLC50428 Me4
- SLC to Judson Smith, 12 February 1901 · New York, N.Y · UCCL12983 Me4
- SLC to Albert Bigelow Paine, 16 November 1901 · Riverdale, N.Y · UCCL12984 Me4, CU-MARK
- Katharine I. Harrison to SLC, 18 April 1902 · New York, N.Y. · UCLC33439 Me4
- Henry H. Rogers to SLC, 16 August 1902 · Poland Springs, Maine · UCLC33521 Me4
- SLC to Edward W. Ordway, 4 January 1903 · Riverdale, N.Y · UCCL12871 Me4
- Albert Bigelow Paine to SLC, 17 August 1904 · New York, N.Y. · UCLC50426 Me4
- SLC per Isabel V. Lyon to Albert Bigelow Paine, 19 August 1904 · Lee, Mass · UCCL12989 Me4
- Albert Bigelow Paine to SLC, 19 August 1904 · New York, N.Y. · UCLC50427 Me4
- SLC to Louise Paine, 4 November 1908 · Redding, Conn · UCCL08151 Me4
- SLC to Louise Paine, 9 October 1909 · Redding, Conn · UCCL12973 Me4
- SLC to Louise Paine, 17 December 1909 · Hamilton, Bermuda · UCCL12975 Me4
- SLC to Louise Paine, 23 February 1910 · Hamilton, Bermuda · UCCL02275 Me4
- SLC to Louise Paine, 24 February 1910 · Hamilton, Bermuda · UCCL12977 Me4
- SLC to Louise Paine, 24 March 1910 · Hamilton, Bermuda · UCCL02321 Me4
- SLC to Louise Paine, Unknown date, New York, N.Y · UCCL12992 Me4
- SLC to Albert Bigelow Paine, Unknown date, Redding, Conn · UCCL12991 Me4
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