Subject Region
United States
252
Great Britain
31
India
21
China
18
Australia
15
Canada
14
Africa
13
Asia
12
Antarctica
7
Germany
7
South Africa
7
Japan
5
Singapore
5
Costa Rica
4
Developing countries
4
Latin America
4
Soviet Union
4
Texas
4
Boston
3
Chile
3
Iraq
3
Malaysia
3
Massachusetts
3
Mexico
3
Tennessee River Valley
3
Canada, Eastern
2
Confederate States of America
2
European Union countries
2
France
2
Greece
2
Guiana
2
Hong Kong
2
Iran
2
Kenya
2
Korea
2
Korea (South)
2
Middle East
2
Minnesota
2
New England
2
New York (State)
2
Nigeria
2
Northeastern States
2
Palestine
2
Portugal
2
Rome
2
Samoa
2
America Latina
1
Angola
1
Argentina
1
Belgium
1
more ...