applic articl sixth council direct ad tax author derog context draft convent itali switzerland eec letter date juli italian govern inform commiss pursuant provis intent introduc nation law derog sixth direct context draft convent itali austria mainten frontier countri replac convent sign vienna februari final import materi mainten work temporari import motor vehicl tool equip work exempt vat commiss inform member state italian govern intent letter date septemb accord articl sixth direct council decis author derog deem adopt month member state inform laid previou paragraph matter rais council matter rais period council decis deem adopt novemb oj