Commission Regulation (EEC) No 2978/78 of 15 December 1978 re-establishing the levying of customs duties on thermionic, cold cathode and photo-cathode valves and tubes, etc., falling within subheadings 85.21 A, B and C and originating in developing countries, to which the preferential tariff arrangements set out in Council Regulation (EEC) No 2705/77 apply