APA (7th ed.) Citation

John, G., & Humphry, D. (1971). Because they're black. Penguin Books.

Chicago Style (17th ed.) Citation

John, Gus, and Derek Humphry. Because They're Black. Harmondsworth: Penguin Books, 1971.

MLA (9th ed.) Citation

John, Gus, and Derek Humphry. Because They're Black. Penguin Books, 1971.