Season 1 PBS , 1970 - 1971 Season 2 PBS , 1971 - 1972 Season 3 PBS , 1972 - 1973 Season 4 PBS , 1973 - 1974 Season 5 PBS , 1974 - 1975 Season 6 PBS , 1976 Season 7 PBS , 1976 Season 8 PBS , 1978