von Humboldt, Alexander. «Humboldt Requests a Passport from James Madison and the Return of His Maps from Gallatin». A: Moheit, Ulrike. Alexander von Humboldt: Briefe aus Amerika. 1799–1804. Berlín: Akademie Verlag, 1993, p. 298. «... I feel I will return to this beautiful country in a few years. The path from the Missouri to the Pacific Ocean will then be open... Through the same courier, I entreated Mr. Gallatin to remember my maps of Mexico.»
von Humboldt, Alexander. «Humboldt Envisions Promising Discoveries in the West but Sees Great Dangers in the Importation of African Blacks». A: Moheit, Ulrike. Alexander von Humboldt: Briefe aus Amerika. 1799–1804. Berlín: Akademie Verlag, 1993.
worldcat.org
Canal-Soler, Jordi «Humboldt, el naturalista que redescubrió América». Historia National Geographic [Barcelona], 132, 2015, pàg. 10-14. ISSN: 1696-7755 [Consulta: 5 juny 2019].
Canal-Soler, Jordi «Humboldt, el naturalista que redescubrió América». Historia National Geographic [Barcelona], 132, 2015, pàg. 10-14. ISSN: 1696-7755 [Consulta: 5 juny 2019].
Humboldt, Alexander von Del Orinoco a l'Amazones. Traducció: Adolf Meyer-Abich. Guadarrama, 1982, p. 388. OCLC978360121.
