Region
United States --
33
United States
15
United states --
9
China --
2
Soviet Union --
2
Afghanistan
1
Afghanistan --
1
Africa
1
Africa --
1
Asia
1
Asia --
1
China
1
Developing countries
1
Developing countries --
1
Europe, Eastern
1
Europe, Eastern --
1
Foreign countries
1
Great Britain --
1
Iran
1
Iran --
1
Japan
1
Japan --
1
Middle East
1
Middle East --
1
Soviet Union
1