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3. Pat. 2335682 (France) -Bull. Off. Prop. Industr., 1975, Pat. 2235682 (France) -Bull, Off. Prop. Industr., 1975, No. 10, p. 2938
4. Pat. 599918 (Switzerland) -Schweiz. Patenblatt, 1978, No. 24, p. 1348
5. Pat. 2432392 (FRG) -Auszüge aus der Auslegeschriften, 1977, No. 35, p. 3067.