APA (7th ed.) Citation

Koestler, A. (1964). The sleepwalkers: A history of man's changing vision of the universe. Penguin Books.

Chicago Style (17th ed.) Citation

Koestler, Arthur. The Sleepwalkers: A History of Man's Changing Vision of the Universe. Harmondsworth, Middlesex: Penguin Books, 1964.

MLA (8th ed.) Citation

Koestler, Arthur. The Sleepwalkers: A History of Man's Changing Vision of the Universe. Penguin Books, 1964.