Regulation (EEC) No 600/74 of the Commission of 15 March 1974 re-establishing the levying of the customs duties on tubes and pipes and blanks therefor, of copper; hollow bars of copper, falling within heading No 74.07 originating in Yugoslavia to which the preferential tariff arrangements set out in Council Regulation (EEC) No 3501/73 of 18 December 1973 apply