[1940,1942]
[1943,1945]
[1946,1948]
[1949,1951]
[1952,1954]
[1955,1957]
[1958,1960]
[1961,1963]
[1964,1966]
[1967,1969]
[1970,1972]
[1973,1975]
[1976,1978]
[1979,1981]
[1982,1984]
[1985,1987]
[1988,1990]
[1991,1993]
[1994,1996]
[1997,1999]