1. K. Nakanishi: “The Unknown Reality of Rare Earths,” ECO JAPAN Report, Nikkei Ecol., Nov. 15, 2010. http://eco.nikkeibp.co.jp/article/report/20101112/105248/ (in Japanese).
2. T.H. Okabe and K. Nose: Waste Manag. Res., 2011, vol. 22, pp. 403–11 (in Japanese).
3. M. Sagawa, ed.: in All about Neodymium Magnets, AGNE Gijutsu Center Inc., Tokyo, 2011 (ISBN 978-4-901496-58-2 C3054) (in Japanese).
4. T.H. Okabe and K. Nose, eds.: in The Latest Technological Trend of Rare Metals, CMC Publishing, Tokyo, 2012, p. 316 (in Japanese).
5. S. Shirayama and T.H. Okabe: J. Soc. Automot. Eng. Jpn., 2011, vol. 65, pp. 87–94 (in Japanese).