Singleton, D., & Ryan, L. (2004). Language acquisition: The age factor (2nd ed.). Multilingual Matters Ltd..
Lua i Stíl Chicago (17ú heag.)Singleton, David, agus Lisa Ryan. Language Acquisition: The Age Factor. 2nd ed. Clevedon: Multilingual Matters Ltd., 2004.
Lua MLA (9ú heag.)Singleton, David, agus Lisa Ryan. Language Acquisition: The Age Factor. 2nd ed. Multilingual Matters Ltd., 2004.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.