1. H.C. Hoover and L.H. Hoover, De Re Metallica, by Georgius Agricola (NewYork: Dover Publications Inc., 1950), Book VI.
2. Anon, Cobalt Facts-History (Guildford, Surrey, U.K.: The Cobalt Development Institute, 2007).
3. T. Åkre, “Electrowinning of Cobalt from Chloride Solutions: Anodic Deposition of Cobalt Oxide on DSA” (Doctoral thesis, Norwegian University of Science and Technology, Trondheim, Norway, 2008).
4. P.E. Queneau, “Cobalt and the Nickeliferous Limonites” (Doctoral thesis, Delft University of Technology, The Netherlands, 1971).
5. Monograph Series,1960