1. Emsley J., Nature's Building Blocks: An A-Z Guide to the Elements (Oxford, England: Oxford University Press 2001)
2. Navarro J., Zhao F., 2 1-17. http://home.3frontiersin.org/ (2014)
3. Castor S.B., Hedrick J.B., Rare Earth Elements, Industrial Minerals and Rocks (Edited by Jessica Elzea Kogel, Nikhil C. Trivedi and James M. Barker. Society for Mining, Metallurgy and Exploration. http://www.rareelementresources.com/i/pdf/RareEarths-CastorHedrickIMAR7.pdf, 769-792, 2006)
4. Towards zero-waste valorisation of rare-earth-containing industrial process residues: a critical review
5. Curran M.A., Cincinnati, OH: National Risk Management Research Laboratory, Office of Research and Development, US Environmental Protection Agency (2006)