Changes made by Commission Regulation (EEC) No 888/93 of 15 April 1993 amending Commission Regulation (EEC) No 1760/83 on special detailed rules for the application of the system of advance- fixing certificates for certain agricultural products exported in the form of goods not covered by Annex II to the Treaty: Commission Regulation (EEC) No 1760/83 of 29 June 1983 on special detailed rules for the application of the system of advance-fixing certificates for certain agricultural products exported in the form of goods not covered by Annex II to the Treaty and derogating from Regulation (EEC) No 2730/79 with regard to payment of refunds on butter