Changes to 83/138/EEC: Commission Decision of 25 March 1983 concerning certain measures to prevent the spread of African swine fever
EU Decision 1983/138
Made by 83/300/EEC: Commission Decision of 8 June 1983 amending Decision 83/138/EEC concerning certain health protection measures against African swine fever
From legislation.gov.uk's record of changes, the official one: see it there.