1. T.H. Okabe and J. Kang: The Latest Technological Trend of Rare Metals, CMC, Tokyo, 2012, pp. 83–94.
2. J. Kang and T.H. Okabe: Metall. Mater. Trans. B., 2013, vol. 44B, pp. 516–27.
3. J. Gambogi: Mineral Commodity Summaries 2020, US Geological Survey, Reston, 2020, pp. 174–75. https://pubs.usgs.gov/periodicals/mcs2020/mcs2020-titanium.pdf
4. J. Gambogi: Mineral Commodity Summaries 2010, US Geological Survey, Reston, 2010, pp. 174–75. https://s3-us-west-2.amazonaws.com/prd-wret/assets/palladium/production/mineral-pubs/titanium/mcs-2010-titan.pdf
5. E.L. Bray: Mineral Commodity Summaries 2020, US Geological Survey, Reston, 2020, pp. 20–21. https://pubs.usgs.gov/periodicals/mcs2020/mcs2020-aluminum.pdf