Commission Regulation (EEC) No 1509/91 of 4 June 1991 amending Regulation (EEC) No 3879/90 laying down rules for implementing the import arrangements applicable to products falling within CN codes 0714 10 10, 0714 10 91 and 0714 10 99, originating in Thailand and exported from that country in 1991, 1992, 1993 and 1994