Region
Soviet Union --
22
Soviet Union
15
United States --
7
United States
5
Europe --
3
Europe, Eastern
3
Europe, Eastern --
3
Asia
2
Asia --
2
Afghanistan
1
Afghanistan --
1
Africa, Southern --
1
Caribbean Area --
1
Developing countries
1
Eastern Europe
1
Germany
1
Germany --
1
Japan
1
Japan --
1
United states --
1