Region
United States --
13
United States
11
Developing countries --
5
Developing countries
4
Great Britain
4
Great Britain --
4
Soviet Union
4
Germany --
3
Soviet Union --
3
United states --
3
Asia, Southeastern --
2
Europe --
2
Middle East --
2
20th Century
1
Afghanistan --
1
Africa --
1
Africa, Northeast
1
Asia, Southeastern
1
Australia
1
Australia --
1
Caucasus, Northern
1
Central America
1
East Asia
1
East Asia --
1
Eurasia --
1
Europe
1
Germany
1
Latin America --
1
Russia(Federation) --
1
United States - --
1