South America, the green world of the naturalists. Five centuries of natural history in South America. Selected and annnotated with biographical sketches ans introduction.
A. v. Humboldt S. 145 - 164: The Cavern of the Guacharo and the electric eel.
Bild: Humboldt am Orinoco. Gem. von Weitsch 1806. hier: "By Youn g"! Taf. Nach S. 158.
Hagen, Victor Wolfgang von: South America, the green world of the naturalists. Five centuries of natural history in South America. Selected and annnotated with biographical sketches ans introduction., London: Eyre & Spottiswoode, 1951, 398 markieren