1. Extractive Metallurgy of Niobium;Gupta,1994
2. Rembar Molybdenum Technical Information, The Rembar Company, Inc., NY, USA.
3. Ulmans Encyklopadie der Technischen Chemie;Dautzenberg,1974
4. Ulmans Encyclopedia of Industrial Chemistry, vol. Al;Hall,1985
5. The Theory of Metallurgical Processes;Fillipov,1975