Coba jelasin This in turn cites: dari Alexander Melville Bell dalam bahasa melayu dong

John Hitz, Alexander Melville Bell (Washington, 1906).

Encyclopædia Britannica. Alexander Graham Bell, Encyclopædia Britannica, 2010. Encyclopædia Britannica Online. 24 May. 2010.

Winzer, Margret A. The History Of Special Education: From Isolation To Integration, Gallaudet University Press, 1993, ISBN 1-56368-018-1, ISBN 978-1-56368-018-2.