1. Nickel, Encyclopaedia Britannica,1989
2. Extractive Metallurgy of Nickel, Cobalt and Platinum-Group Metals;Crundwell,2011
3. Handbook of Extractive Metallurgy;Kerfoot,1997
4. Anorganische Chemie, Walter de Gruyter & Co (10. Auflage) Berlin, New York;Riedel,2010