Butterfield, H. (1981). The origins of history (First edition.). Basic Book Inc. Publisher.
Lua i Stíl Chicago (17ú heag.)Butterfield, Herbert. The Origins of History. First edition. New York: Basic Book Inc. Publisher, 1981.
Lua MLA (8ú heag.)Butterfield, Herbert. The Origins of History. First edition. Basic Book Inc. Publisher, 1981.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.