1. 1) A. Cowley: PGM Market Report May 2020, (Johnson Matthey Plc., 2020). http://www.platinum.matthey.com/services/market-research (accessed 2021-01-18).
2. 2) Johnson Matthey website. http://www.platinum.matthey.com/ (accessed 2021-01-18).
3. 3) F. Habashi (ed.): Handbook of Extractive Metallurgy vol. III, (Wiley-VCH, Weinheim, 1997) pp. 1269-1326.
4. 4) F. Crundwell, M. Moats, V. Ramachandran, T. Robinson and W.G. Davenport: Extractive Metallurgy of Nickel, Cobalt and Platinum Group Metals (Elsevier, Oxford, 2011).
5. 5) S. Seetharaman (ed.): Treatise on Process Metallurgy, Volume 3: Industrial Processes, (Elsevier, London, 2013) pp. 1071-1097.