APA (7th ed.) Citation

Fried, J., Lewis, P., & Fried, J. (2016). Charlemagne. Harvard University Press.

Chicago Style (17th ed.) Citation

Fried, Johannes, Peter Lewis, and Johannes Fried. Charlemagne. Cambridge, Massachusetts ; London, England: Harvard University Press, 2016.

MLA (9th ed.) Citation

Fried, Johannes, et al. Charlemagne. Harvard University Press, 2016.