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Dyfyniad Arddull ChicagoVincent. The Power of Positive Thinking Peale, Norman. Boston: Harvard Business Review, 1980.
Dyfyniad MLAVincent. The Power of Positive Thinking Peale, Norman. Harvard Business Review, 1980.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.