1. Transition metal carbides and nitrides, Toth, L.E.. New York: Academic Press 1971
2. Westbrook, J.H., Stover, E.R.: In: High-temperature materials and technology. Campbell, I.E., Shrewood, E.M., (eds.), p. 312. New York: Wiley 1967
3. Ern, V., Switendick, A.C.: Phys. Rev.137A, 1927 (1965)
4. Lye, R.G., Logothetis, E.M.: Phys. Rev.147, 622 (1966)
5. Conklin, J.B. Jr., Silversmith, D.J.: Int. J. Quantum Chem.IIa, 243 (1968)