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Dyfyniad Arddull ChicagoFreeman, Christopher. Longwaves in the World Economy. London: Butterworths, 1983.
Dyfyniad MLAFreeman, Christopher. Longwaves in the World Economy. London: Butterworths, 1983.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.