1Thomas Jefferson to Alexander von Humboldt, 6 March 1809 (Jefferson Papers)
Humboldt, Friedrich Wilhelm Heinrich Alexander, Baron von; letters to [index entry]
2Thomas Jefferson to Alexander von Humboldt, 14 April 1811 (Jefferson Papers)
Humboldt, Friedrich Wilhelm Heinrich Alexander, Baron von; letters to [index entry]
3Thomas Jefferson to Alexander von Humboldt, 6 December 1813 (Jefferson Papers)
Humboldt, Friedrich Wilhelm Heinrich Alexander, Baron von; letters to [index entry]
4Thomas Jefferson to Alexander von Humboldt, 13 June 1817 (Jefferson Papers)
Humboldt, Friedrich Wilhelm Heinrich Alexander, Baron von; letters to [index entry]