unknown 1953 1958 1959 1960 1961 1962 1964 1966 1968 1970 1971 1972 1973 1975 1976 1978 1979 1980 1981 1982 1984 1985 1986 1987 1988 1990 1991 1992 1993 1994 1995 1996 1997 1999 2000 2001 2002 2003 2004