1. C. Bodsworth:The Extraction and Refining of Metals, 1st ed., CRC Press Inc., Boca Raton, FL, 1994, pp. 44–46.
2. J.R. Boldt, Jr.: inThe Winning of Nickel: Its Geology, Mining and Extractive Metallurgy, 1st ed., Paul Queneau, ed., Methuen & Co. Ltd., London, 1967, pp. 227–88.
3. Cobalt Monograph, prepared in collaboration with Battelle Memorial Institute, Colombus, OH, Centre D’Information du Cobalt, Brussels, 1960, pp. 33–42.
4. O. Kubaschewski and C.B. Alcock:Metallurgical Thermochemistry, 5th ed., Pergammon Press, Oxford, United Kingdom, 1979, p. 400.
5. 1994 Britannica Book of the Year, Encyclopedia Britannica Inc., Chicago, IL, 1994, pp. 578–579 and 583.