Ogundipe P. A. & Tregidgo P. S. (1974). Practical English: A comprehensive secondary course. Book four. Longman.
Lua i Stíl Chicago (17ú heag.)Ogundipe P. A. agus Tregidgo P. S. Practical English: A Comprehensive Secondary Course. Book Four. England: Longman, 1974.
Lua MLA (9ú heag.)Ogundipe P. A. agus Tregidgo P. S. Practical English: A Comprehensive Secondary Course. Book Four. Longman, 1974.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.