1. A. Neckel, in: R. Freer (Ed.), The Physics and Chemistry of Carbides, Nitrides and Borides, Kluwer, Dordrecht, 1990, p. 458.
2. R.J. Meyer, E.H.E. Pietsch. Gmelins Handbooks of Inorganic Chemistry, Vol. 41, 8th ed., Springer, Berlin, 1951, p. 357.
3. K.J.A. Brookes, World Directory and Handbook of Hard Metals and Hard Materials, International Carbide Data, East Barnet, Hertfordshire, UK, 5th ed., 1992.
4. C. K. Narula. Ceramic Precursor Technology and Its Application. Marcel Dekker, New York, 1995, p. 235.