1. A. G. Merzhanov, V. M. Shkiro andI. P. Borovinskaya, “Synthesis of refractory inorganic compounds”, of refractory compounds' (Noyes, New Jersey, USA, 1985).
2. Idem., French Pat. 2088 668 (1972).
3. Idem., US Pat. 3726 643 (1973).
4. Idem., UK Pat. 1321 084 (1974).
5. Idem.,Japan Pat. 1098 839 (1982).