1. Jaskula B.W., in Mineral Commodity Summaries 2019, ed. by USGS (Reston, Virginia, 2019), p. 62
2. Mathieux F., Ardente F., Bobba S., Nuss P., Blengini G., Alves-Dias P., Blagoeva D., Torres-DeMatos C., Wittmer D., Pavel C., Hamor T., Saveyn H., Gawlik B., Orveillon G., Huygens D., Garbarino E., Tzimas E., Bouraoui F., Solar S., Critical raw materials and the circular economy – background report (Publications Office of the European Union, Luxembourg, 2017), pp. 39-40.
3. Anderson C.S., in Mineral Commodity Summaries 2019, ed. by USGS (Reston, Virginia, 2019), p. 78
4. European Commission, Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions on the 2017 list of Critical Raw Materials for the EU. (COM(2017) 490 final, 2017)
5. The U.S. Department of the Interior, Final List of Critical Minerals 2018 (Federal Register 83 (97) 2018)