COMMON CUSTOMS TARIFF - GENERALIZED PREFERENCE SCHEME IN FAVOUR OF DEVELOPING COUNTRIES - SUSPENSION OF CUSTOMS DUTIES UP TO A CERTAIN CEILING - CERTIFICATE OF ORIGIN OF GOODS - PRODUCTION AFTER RE-INTRODUCTION OF CUSTOMS DUTIES - NO ENTITLEMENT TO EXEMPTION ( COUNCIL REGULATION NO 2789/79 , ART . 1 ( 3 ) AND ART . 3 ( 1 ) AND ( 2 ))