Cita APA (7th ed.)

Kellner, L. (1963). Alexander von Humboldt. Oxford University Press.

Cita Chicago (17th ed.)

Kellner, L. Alexander Von Humboldt. London, New York: Oxford University Press, 1963.

Cita MLA (8th ed.)

Kellner, L. Alexander Von Humboldt. Oxford University Press, 1963.