Cita APA (7th ed.)

Gasser, M., & Killer, P. (1970). Alexander von Humboldt. Conzett & Huber.

Cita Chicago (17th ed.)

Gasser, Manuel, i Peter Killer. Alexander Von Humboldt. Zürich: Conzett & Huber, 1970.

Cita MLA (8th ed.)

Gasser, Manuel, i Peter Killer. Alexander Von Humboldt. Conzett & Huber, 1970.