Council Regulation (EU) No 1257/2010 of 20 December 2010 extending the temporary derogation measures from Regulation No 1 of 15 April 1958 determining the languages to be used by the European Economic Community and Regulation No 1 of 15 April 1958 determining the languages to be used by the European Atomic Energy Community introduced by Regulation (EC) No 920/2005