1. V. Zepf, in Rare earth elements: A new approach to the nexus of supply, demand and use: exemplified along the use of neodymium in permanent magnets, Springer, Berlin (2013).
2. D. Bauer, D. Diamond, J. Li, D. Sandalow and P. Telleen, Technical Report: U. S. Department of Energy Critical Materials Strategy, December (2011).
3. N. V. Thakur, D. V. Jayawant, N. S. Iyer and K. S. Koppiker, Hydrometallurgy, 34(1), 99 (1993).
4. Y. A. El-Nadi, Hydrometallurgy, 119-120, 23 (2012).
5. M. S. Lee, J. Y. Lee, J. S. Kim and G. S. Lee, Sep. Purif. Technol., 46(1-2), 72 (2005).