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Dyfyniad Arddull ChicagoAmerican Government: Principles and Practices. USA: McGraw-Hill, 1996.
Dyfyniad MLAAmerican Government: Principles and Practices. USA: McGraw-Hill, 1996.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.