1978 April 8 1978 April 15 1978 June 24 1979 January 27 1979 April 7 1979 June 5 1979 June 19 1980 March 8 1980 April 21 1982 April 21 1982 April 26 1986 April 12 1986 August 6 1989 March 7 1989 May 16 1989 July 3 1991 July 23 1994 June 7 1989 February 24