Obee, B. (1998). Cambridge first certificate: Grammar and usage. Cambridge University Press.
Lua i Stíl Chicago (17ú heag.)Obee, Bob. Cambridge First Certificate: Grammar and Usage. Cambridge: Cambridge University Press, 1998.
Lua MLA (8ú heag.)Obee, Bob. Cambridge First Certificate: Grammar and Usage. Cambridge University Press, 1998.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.