Region
United States --
6
United States
4
Great Britain
2
Great Britain --
2
Soviet Union
2
Soviet Union --
2
Developing countries
1
Germany
1
Germany (East)
1
Germany (East) --
1
Germany (West)
1
Germany (West) --
1
Germany --
1
Russia
1
Russia --
1
Spain --
1
United states --
1
Yugoslavia
1
Yugoslavia --
1