APA (7th ed.) Citation

Keen,Maurice. (1991). The Penguin history of Medieval Europe. Penguin Books.

Chicago Style (17th ed.) Citation

Keen,Maurice. The Penguin History of Medieval Europe. Penguin Books, 1991.

MLA (9th ed.) Citation

Keen,Maurice. The Penguin History of Medieval Europe. Penguin Books, 1991.

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