APA (7th ed.) Citation

Runciman, S. S. (1951). A history of the Crusades. Penguin Books.

Chicago Style (17th ed.) Citation

Runciman, Steven Sir. A History of the Crusades. London: Penguin Books, 1951.

MLA (9th ed.) Citation

Runciman, Steven Sir. A History of the Crusades. Penguin Books, 1951.

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