1Thomas Jefferson to Henry Guegan, 27 August 1820 (Jefferson Papers)
Vos, Gerrit Jansz; Gerardi Joannis Vossii Etymologicon Linguæ Latinæ [index entry]
2Henry Guegan to Thomas Jefferson, 9 September 1820 (Jefferson Papers)
Vos, Gerrit Jansz; Gerardi Joannis Vossii Etymologicon Linguæ Latinæ [index entry]