Butterfield, H., & Watson, A. The origins of history. London.
Dyfyniad Arddull ChicagoButterfield, Herbert, and Adam Watson. The Origins of History. c1981: London.
Dyfyniad MLAButterfield, Herbert, and Adam Watson. The Origins of History. London.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.