1. Whoriskey, P. In Your Phone, In Their Air. The Washington Post (2 October 2016).
2. Amnesty International. Time to Recharge: Corporate Action and Inaction to Tackle Abuses in the Cobalt Supply Chain (Amnesty International, 2017).
3. Freeman, G. K .W. Process for recovery of cobalt by selective precipitation of cobalt-calcium double salt. US patent US6264904B1 (2001).
4. British Geological Survey. Cobalt Commodity Profile (BGS, 2009).
5. US Geological Survey. Mineral Commodity Summaries 2018 (USGS, 2018).