APA (7th ed.) Citation

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

Chicago Style (17th ed.) Citation

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

MLA (8th ed.) Citation

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

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