APA (7th ed.) Citation

Koestler, A. (1966). Darkness at noon. Penguin.

Chicago Style (17th ed.) Citation

Koestler, Arthur. Darkness at Noon. Harmondsworth Middlesex: Penguin, 1966.

MLA (9th ed.) Citation

Koestler, Arthur. Darkness at Noon. Penguin, 1966.