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| 1968 | 1969 | 1971 | 1974 | 1975 |
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| 1976a | 1976b | 1978a | 1978b | 1979 |
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| 1981 | 1982a | 1982b | 1983a | 1983b |
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| 1984 | 1985* | 1987 | 1988 | 1990a |
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| 1990b | 1990c | 1991a | 1991b | |