Langan, J. (1981). English Skills (2nd ed.). McGraw-Hill.
Lua i Stíl Chicago (17ú heag.)Langan, John. English Skills. 2nd ed. New York: McGraw-Hill, 1981.
Lua MLA (9ú heag.)Langan, John. English Skills. 2nd ed. McGraw-Hill, 1981.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.