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Dyfyniad Arddull ChicagoSchell, Erwin Haskell. Technique of Executive Control. 8th ed. New York: McGraw-Hill, 1957.
Dyfyniad MLASchell, Erwin Haskell. Technique of Executive Control. 8th ed. McGraw-Hill, 1957.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.