1. a U.S. 3,007,991 (1961); U.S. 3,009,979 (1961); U.S. 3,314,820 (1967); U.S. 3,706,601 (1972); U.S. 3,898,099 (1974); U.S. 4,000,005 (1976); U.S. 3,184,820 (1965); U.S. 3,009,980 (1961); Ger. 1,187,698 (1960); Brit. 1,208,322 (1967); Fr. 1,314,528 (1962); Fr. 2,166,105 (1973); Czech. 176,569 (1979); Czech. 167,146 (1977)