1. Zelikman , A. N. , Krein , O. E. and Samsonov , G. V. [Metallurgy of Rare Metals] , 2nd edition , Israel Program for Scientific Translation , Jerusalem . 1966 ( available from NTIS, US Dept. of Commerce, Springfield Va 22151 ) .
2. Extractive metallurgy of niobium, tantalum, and vanadium