Roberts, J. M. (1967). Europe, 1880-1945. Longmans.
Lua i Stíl Chicago (17ú heag.)Roberts, John Morris. Europe, 1880-1945. London: Longmans, 1967.
Lua MLA (9ú heag.)Roberts, John Morris. Europe, 1880-1945. Longmans, 1967.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.