MLA

Runciman, Steven. A History of the Crusades. 1 : The First Crusade and the Foundation of the Kingdom of Jerusalem. Cambridge (Mass.): University press, 1951.

APA

Runciman, S. (1951). A history of the crusades. 1 : The first crusade and the foundation of the kingdom of Jerusalem. Cambridge (Mass.): University press.

Chicago

Runciman, Steven, A History of the Crusades. 1 : The First Crusade and the Foundation of the Kingdom of Jerusalem. Cambridge (Mass.): University press, 1951.