Region
Europe --
United States --
12
United States
10
Europe
8
Canada --
2
European Economic Community countries
2
European Economic Community countries --
2
Soviet Union --
2
Canada
1
Developing countries
1
Japan - --
1
Japan --
1
Russia (Federation)
1
Russia (Federation) --
1
Soviet Union
1
United States - --
1
United states --
1