Tignor, R. L. (2014). Worlds together, worlds apart, volume 1: Beginnings through the fifteenth century (Fourth edition.). W. W. Norton and Company.

Tignor, Robert L. Worlds Together, Worlds Apart, Volume 1: Beginnings Through the Fifteenth Century. Fourth edition. New York ; London: W. W. Norton and Company, 2014.

Tignor, Robert L. Worlds Together, Worlds Apart, Volume 1: Beginnings Through the Fifteenth Century. Fourth edition. W. W. Norton and Company, 2014.