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2. 2) Industiral Rare Metal, Annual Review, Arumu Pub., Tokyo, No. 129, p. 40 (2013); No. 130, p. 42 (2014); No. 131, p. 38 (2015); No. 132, p. 46 (2016); No. 133, p. 37 (2017); No. 134, p. 39 (2018); No. 135, p. 46 (2019); No. 136, p. 38 (2020). [in Japanese]
3. 3) M. Sagawa, ed., All about Neodymium Magnets, AGNE Gijutsu Center Inc., Tokyo, p. 161 (2011). [in Japanese]
4. 4) US Geological Survey, Mineral Commodity Summaries, USGS (2020).
5. 5) O. Takeda, E. Nakamura, and Y. Sato, Rare Metal Handbook, Vol. I. (Ed. G. Adachi), Maruzen, Tokyo, p. 217 (2011). [in Japanese]