1. C. Heid, D. Hoffmann, J. Polster, Ger. Patent 2,233,941 (1974; Chem. Abs. 81,79,674b (1974).
2. J. Mondt, Ger. Patent 3,128,143 (1983);
3. Chem. Abs. 98, 145 138j (1983).
4. W. Bloech, Ger Patent 1,254,150 (1967);
5. Chem. Abs. 68, 49 763u (1967).