Changes made by Commission Regulation (EEC) No 1305/80 of 29 May 1980 amending for the 13th time Regulation (EEC) No 2044/75 in connection with the export licence for butter and derogating from Regulation (EEC) No 2730/79 in connection with payment of the refund for butter and amending Regulation (EEC) No 210/69: Regulation (EEC) No 2044/75 of the Commission of 25 July 1975 on special detailed rules for the application of the system of import and export licences and the advance fixing of refunds in respect of milk and milk products