• 1972 to 1974 2
• 1975 to 1976 3
• 1977 to 1979 5
• 1980 to 1981 4
• 1982 to 1984 3
• 1985 to 1986 3
• 1987 to 1989 2
• 1990 to 1991 1
• 1992 to 1994 1