Voight, R. C. (1971). Invitation to learning: The learning center handbook. Acropolis Books.
Lua i Stíl Chicago (17ú heag.)Voight, Ralph Claude. Invitation to Learning: The Learning Center Handbook. Washington: Acropolis Books, 1971.
Lua MLA (9ú heag.)Voight, Ralph Claude. Invitation to Learning: The Learning Center Handbook. Acropolis Books, 1971.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.