1. Lanthanides, Tantalum and Niobium,Proceedings of a Workshop in Berlin. (Springer Verlag. Special Public. no 7. Soc. For Geology Applied to Mineral Deposits, 1986).
2. E.C. Bain, H.W. Paxton: Alloying elements in steel, (Handbook American Society of Metals, Park, Ohio, 1966 ).
3. K.A. Gschneider Jr, B.J. Beaudry. Mischmetal Handbook. (American Society of Metals, Park, Ohio, 1979 ) p. 770.
4. J. Scherzer, J.L. Bas, F.D. Hunter: J. Phys. Chem. 79, 1194 (1975).
5. A. Paul: Chemistry of Glasses ( Chapman and Hall, London, 1982 ).