APA (7th ed.) Citation

Koestler, A. (1946). Darkness at noon (5th impression.). Penguin Books.

Chicago Style (17th ed.) Citation

Koestler, Arthur. Darkness at Noon. 5th impression. Harmondsworth [etc.]: Penguin Books, 1946.

MLA (9th ed.) Citation

Koestler, Arthur. Darkness at Noon. 5th impression. Penguin Books, 1946.

Warning: These citations may not always be 100% accurate.