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2. Australian Patent No. 62, 296 (1960);
3. British Patent No. 889, 196 (1962).
4. R. Guglielmetti and J. Metzger, Bull. Soc. Chim. France, 3329 (1969).
5. A. I. Kipriyanov, Usp. Khim., 29, 1337 (1960).