1. I. L. Knunyants, Yu. A. Cheburkov, and A. M. Platoshkin, Author's Certificate No. 203675 (Nov. 16, 1967);
2. Byul. Izobret., No. 21, 28 (1967).
3. P. Leduc and P. Chabrier, Bull. Soc. Chim. France, 2271 (1963).
4. V. A. Rudenko, A. Ya. Yakubovich, and T. Ya. Nikiforova, Zh. Obshch. Khim.,17, 2256 (1947).
5. R. P. Lastovskii, Zh. Prikl. Khim.,19, 440 (1946).