1. Angerer D. G. F. Marscheider-Weidemann A. Lüllmann L. Erdmann D. M. Scharp V. Handke M. Marwede 2009 Raw materials for emerging technologies. A report commissioned by the German Federal Ministry of Economics and Technology http://publica.fraunhofer.de/documents/N-111514.html
2. Bae , J. C. 2000 Strategies and perspectives for securing rare metals in Korea. Critical elements for new energy technologies, an MIT Energy Initiative Workshop Report http://eng.kitech.re.kr/main/
3. National strategies for securing a stable supply of rare earths in different world regions;Barteková;Resources Policy,2016