1. British Patent No. 1,167,105 (1969);
2. Chem. Abstr., 14904g (1970).
3. R. Ohme, E. Schmitz, and P. Dolge, Chem. Ber.,99, 2104 (1966).
4. V. V. Kuznetsov, N. N. Makhova, and L. I. Khmel'nitskii, Izv. Akad. Nauk SSSR, Ser. Khim., No. 9, 2090 (1989).
5. E. Schmitz, Usp. Khim.,45, 54 (1976).