Cita APA (7th ed.)
Verschuur, G. L. (1996). Impact!: The threat of comets and asteroids. Oxford University Press.
Cita Chicago (17th ed.)
Verschuur, Gerrit L. Impact!: The Threat of Comets and Asteroids. New York: Oxford University Press, 1996.
Cita MLA (9th ed.)
Verschuur, Gerrit L. Impact!: The Threat of Comets and Asteroids. Oxford University Press, 1996.
Atenció: Aquestes cites poden no estar 100% correctes.