Era
1945-
34
1990
26
20th century
21
1945
7
20th century --
7
Cases
7
1990-
6
1976-
5
19th century
5
1981-
4
1917
3
1981
3
1981-1993
3
1985-1991
3
1999
3
20th Century
3
Australia
3
Congresses
3
Malaysia
3
1837-1901
2
1925-
2
1945 -
2
1950-
2
1960-
2
1960-1980
2
1966-
2
1971-1981
2
1971-1990
2
1979-
2
1980-
2
1985-1995
2
1986-1991
2
20th century. --
2
Congresses --
2
United States
2
developing countries
2
1750 - 1918
1
1772-1823
1
1775 - 1783
1
1780-1831
1
1783 - 1789
1
1789-1900
1
17th century
1
1800-1837
1
1804-1881
1
1809-1898
1
1853-1910
1
1871-1918
1
1893-
1
18th century
1
more ...