Region
United States --
8
United States
6
Soviet Union --
5
Great Britain
4
Great Britain --
4
Soviet Union
4
China --
2
Russia (Federation) --
2
United states --
2
Asia, Southeastern
1
Asia, Southeastern --
1
China
1
Developing countries
1
Developing countries --
1
Germany
1
Germany --
1
Latin America --
1
Russia (Federation)
1
Spain --
1
United States --
1