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Dyfyniad Arddull ChicagoWhitehouse, Arthur George Joseph. The Sky's the Limit: A History of the U.S. Airlines. New York: Macmillan, 1971.
Dyfyniad MLAWhitehouse, Arthur George Joseph. The Sky's the Limit: A History of the U.S. Airlines. Macmillan, 1971.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.