Schwarz, I. (1991). From Alexander von Humboldt's Correspondence with Thomas Jefferson and Albert Gallatin: Contribution to the 15th Annual Symposion of the Society for German-American Studies Washington, D.C. Georgetown University April 25-28, 1991 / Ingo Schwarz. Alexander von Humboldt Research Center.
Lua i Stíl Chicago (17ú heag.)Schwarz, Ingo. From Alexander Von Humboldt's Correspondence with Thomas Jefferson and Albert Gallatin: Contribution to the 15th Annual Symposion of the Society for German-American Studies Washington, D.C. Georgetown University April 25-28, 1991 / Ingo Schwarz. Berlin: Alexander von Humboldt Research Center, 1991.
Lua MLA (8ú heag.)Schwarz, Ingo. From Alexander Von Humboldt's Correspondence with Thomas Jefferson and Albert Gallatin: Contribution to the 15th Annual Symposion of the Society for German-American Studies Washington, D.C. Georgetown University April 25-28, 1991 / Ingo Schwarz. Alexander von Humboldt Research Center, 1991.