APA (7th ed.) Citation

Riley-Smith, J. S. C. (1977). What were the crusades? Macmillan.

Chicago Style (17th ed.) Citation

Riley-Smith, Jonathan Simon Christopher. What Were the Crusades? London: Macmillan, 1977.

MLA (8th ed.) Citation

Riley-Smith, Jonathan Simon Christopher. What Were the Crusades? Macmillan, 1977.

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