Changes to 93/257/EEC: Commission Decision of 15 April 1993 laying down the reference methods and the list of national reference laboratories for detecting residues
EU Decision 1993/257
Made by Commission Decision of 3 September 1998 establishing the list of national reference laboratories for the detection of residues (notified under document number C(1998) 2487) (98/536/EC)
From legislation.gov.uk's record of changes, the official one: see it there.