APA

Keen M. H., . (19681967). A history of Medieval Europe. New York: F. A. Praeger.

Chicago

Keen Maurice Hugh, . 19681967. A history of Medieval Europe. New York: F. A. Praeger.

Harvard

Keen M. H., . (19681967). A history of Medieval Europe. New York: F. A. Praeger.

MLA

Keen Maurice Hugh, . A history of Medieval Europe. New York: F. A. Praeger. 19681967.