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Dyfyniad Arddull ChicagoStuvel, Gerhard. The Index-number Problem and Its Solution. Basingstoke: Macmillan, 1989.
Dyfyniad MLAStuvel, Gerhard. The Index-number Problem and Its Solution. Macmillan, 1989.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.