1Peter S. Du Ponceau to Thomas Jefferson, 5 December 1817 (Jefferson Papers)
Biddle, Nicholas; and American Philosophical Society [index entry]
2Peter S. Du Ponceau to Thomas Jefferson, 6 January 1818 (Jefferson Papers)
Biddle, Nicholas; and American Philosophical Society [index entry]
3Peter S. Du Ponceau to Thomas Jefferson, 14 April 1818 (Jefferson Papers)
Biddle, Nicholas; and American Philosophical Society [index entry]