1977 December 15 1981 February 2 1982 June 27 1983 September 14 1986 October 26 1989 February 19 1989 April 13 1991 May 12 1994 June 10 1995 August 4 1998 October 15 2001 May 21 2002 April 22 2003 September 24 2006 June 5 2006 July 7 2006 July 12 2009 June 11