Butterfield, H., & Watson, A. The origins of history. London.
Lua i Stíl Chicago (17ú heag.)Butterfield, Herbert, agus Adam Watson. The Origins of History. c1981: London.
Lua MLA (8ú heag.)Butterfield, Herbert, agus Adam Watson. The Origins of History. London.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.