1. U.S. Geological Survey: Mineral Commodity Summaries 2014, U.S. Geological Survey, (2014), pp. 172–73.
2. T.H. Okabe and J. Kang: The Latest Technological Trend of Rare Metals, ed., by T.H. Okabe and K. Nose, CMC Publishing Co., Ltd., Tokyo, Japan, (2012), pp. 83–94.
3. N. Nakamura: Molten Salts, 56 (2013), 121–24.
4. M. Guéguin and F. Cardarelli: Miner. Process. Extr. Metall. Rev., 28 (2007), 1–58.
5. K. Borowiec, A.E. Grau, M. Gueguin, and J-F. Turgeon: United States Patent 5830420, (1998).