10 October 1993
4 April 1993
10 October 1992
4 April 1992
9 September 1991
1 January 1991
9 September 1990
10 June 1990
9 September 1989
1 January 1989
9 September 1988
1 January 1988
9 September 1987
4 April 1987
10 October 1986
4 April 1986
10 October 1985
4 April 1985
10 October 1984
4 April 1984
9 September 1983
1 January 1983
9 September 1982
1 January 1982
9 September 1981
1 January 1981
9 September 1980
4 April 1980
9 September 1979
1 January 1979