R221_PS_1964R221_PS_1967R221_PS_1968R221_PS_1969R221_PS_1970R221_PS_1972R221_PS_1974R221_PS_1976R221_PS_1977R221_PS_1978R221_PS_1979R221_PS_1980R221_PS_1981R221_PS_1982R221_PS_1983R221_PS_1984R221_PS_1986R221_PS_1988R221_PS_1989R221_PS_1990