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2. FRG Patent 2 332 343, 1973, Ref. Zh. Khim., 1975, 17O130.
3. FRG Patent 2 332 398, 1973, Ref. Zh. Khim., 1975, 16O185.
4. FRG Patent 2 332 486, 1973, Ref. Zh. Khim., 1975, 23O165.
5. FRG Patent 2 332 487, 1973, Ref. Zh. Khim., 1975, 17O131.