Sjabloon:Citation

Mineral Wealth

14

</ref> The United States Geological Survey estimates that the production increased from 38,700 tonnes in 2005 to 44,500 tonnes in 2006.^[1]<ref name="USGSCS2007">

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↑ Papp, John F.. Niobium (Columbium). USGS 2006 Commodity Summary.

[USGSCS2006-1] Papp, John F.. Niobium (Columbium). USGS 2006 Commodity Summary.

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