APA (7th ed.) Citation

Mayer, H. E., & Gillingham, J. (1988). The Crusades (2nd ed.). Oxford University Press.

Chicago Style (17th ed.) Citation

Mayer, Hans Eberhard, and John Gillingham. The Crusades. 2nd ed. Oxford [etc.]: Oxford University Press, 1988.

MLA (9th ed.) Citation

Mayer, Hans Eberhard, and John Gillingham. The Crusades. 2nd ed. Oxford University Press, 1988.