Jelaskan Pesawat Buatan Douglas dari Douglas Aircraft Company

Boyne, Walter J. The Aircraft Treasures Of Silver Hill: The Behind-The-Scenes Workshop Of The National Air And Space Museum. New York: Rawson Associates, 1982. ISBN 0-89256-216-1.

Donald, David, ed. Encyclopedia of World Aircraft. Etobicoke, Ontario: Prospero Books, 1997. ISBN 1-85605-375-X.