1. E. K. Storms, ?The refractory carbides?, edited by J. L. Margrave (Academic, New York and London 1967) p. 61.
2. E. R-,St. WindischandC. E. Brukl, ?Planseeberichte f�r Pulvermetallurgie?, Vol. 16 (1968) p. 3?33.
3. B. Aronson andL. J. Aschan, in Proceedings of the International Symposium ?Niobium 81?, San Francisco, California, November 1981, edited by H. Stuart (Metals Society of AIME, 1984) pp. 637?652.
4. J. P. Guha andD. Kolar,J. Less-Common Metals 29 (1972) 33.
5. J. Strid andK. E. Easterling,Acta Metall. 33 (1985) 2057.