Changes to Council Directive of 23 July 1990 on the common system of taxation applicable in the case of parent companies and subsidiaries of different Member States (90/435/EEC)
EU Directive 1990/435
Made by Council Directive 2006/98/EC of 20 November 2006 adapting certain Directives in the field of taxation, by reason of the accession of Bulgaria and Romania
From legislation.gov.uk's record of changes, the official one: see it there.