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Dyfyniad Arddull ChicagoSharma, N L., and R K. Sinha. Mineral Economics. 2. New Delhi: Oxford I B H publishing company, 1980.
Dyfyniad MLASharma, N L., and R K. Sinha. Mineral Economics. 2. Oxford I B H publishing company, 1980.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.