Kalvig, Per, and Erika Machacek. “Examining the Rare-Earth Elements (REE) supply– Demand Balance for Future Global Wind Power Scenarios”. GEUS Bulletin 41 (August 15, 2018): 87–90. Accessed June 27, 2022. https://geusbulletin.org/index.php/geusb/article/view/4350.