O'Brien, R. (1980). Machines (2nd ed.). Time-Life Books.
Lua i Stíl Chicago (17ú heag.)O'Brien, Robert. Machines. 2nd ed. Hong Kong: Time-Life Books, 1980.
Lua MLA (9ú heag.)O'Brien, Robert. Machines. 2nd ed. Time-Life Books, 1980.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.