[1940,1943]
[1944,1947]
[1948,1951]
[1952,1955]
[1956,1959]
[1960,1963]
[1964,1967]
[1968,1971]
[1972,1975]
[1976,1979]
[1980,1983]
[1984,1987]
[1988,1991]
[1992,1995]
[1996,1999]