Implementation agreement between the government of the United Kingdom of Great Britain and Northern Ireland and the government of the Russian Federation concerning the partial prepayment of certain debt obligations of the government of the Russian Federation, London, 7 July 2005 and Moscow, 12 July 2005, [and] supplemental implementation agreement between the government of the United Kingdom of Great Britain and Northern Ireland and the government of the Russian Federation concerning the partial prepayment of certain debt obligations of the government of the Russian Federation