Columbia subject headings:
Harvard subject headings:
Humboldt, Alexander von, 1769-1859--Congresses.
Natural history--Congresses
Scientific expeditions--History--19th century--Congresses.
South America--Description and travel--Congresses.
Princeton subject headings:
Humboldt, Alexander von, 1769-1859--Congresses.
Natural history--Congresses.
Scientific expeditions--History--19th century--Congresses.
South America--Description and travel--Congresses.