Communication

1947	1950	1960	1970	1980	1990	2000
	1954	1962	1971	1981	1991	2001
	1956	1963	1972	1982	1992	2002
		1964	1973	1983	1993	2003
		1965	1974	1984	1994	2004
		1966	1975	1985	1995	2005
		1967	1976	1986-1988	1996	2006
		1968	1977	1986	1997	2007
		1969	1978	1987	1998	2008
			1979	1988	1999
				1989