1. W.W. Stephens and H.L. Gilbert: Trans. AIME, 1952, vol. 194, p. 733.
2. C.V. Sundaram and K.S. Subba Rao: Proc. INSA-BARC Winter School on Chemistry and Metallurgy of Rare Metal Extraction, Bhabha Atomic Research Centre, Bombay, 1975, pp. 231–263.
3. O.K. Mehra, S.Z. Hussain, and P.K. Jena: Trans. Ind. Inst. Met., 1966, vol. 19, p. 53.
4. K.R. Srinivasan and P.K. Jena: Trans. Ind. Inst. Met., 1969, vol. 22, pp. 35–40.
5. O.K. Mehra and P.K. Jena: Trans. Ind. Inst. Met., 1967, vol. 20, p. 208.