Commission Regulation (EEC) No 1631/83 of 15 June 1983 imposing a provisional anti-dumping duty on imports of certain glass textile fibres (rovings) originating in Czechoslovakia, the German Democratic Republic and Japan, accepting a price undertaking from one Japanese exporter and terminating the proceeding in respect of imports of certain glass textile fibres (mats), originating in Czechoslovakia and the German Democratic Republic