1. How Hydrometallurgy and the SX/EW Process Made Copper the "Green" Metal 2001 www.copper.org/publications/newsletters/innovations/2001/08/hydrometallurgy.html
2. Horizon 2020 Work Programme 2014 - 2015, Ch. 12 2015 https://ec.europa.eu/research/participants/data/ref/h2020/wp/2014_2015/main/h2020-wp1415-climate_en.pdf
3. Report on critical raw materials for the EU 2014 http://ec.europa.eu/growth/sectors/raw-materials/specific-interest/critical/index_en.htm