"countries whose" is correct and is commonly used in written English.
Example sentence: Countries whose citizens require a visa must submit an application form.
So that's three countries whose manufacturing sectors shrank last month.
Developing countries, whose tariffs tend to be higher, are expected to make deeper cuts.
Stamping it out would help those countries whose resources are being stolen.
It matters because a lot of other countries whose policies challenge these international norms are watching.
And these are rich countries whose economies have held up fairly well.
Donor countries, whose aid makes up 55% of the budget, share these concerns.
Oil-producing countries whose budgets depend on high prices are in particular trouble.
This seems to mean opposition groups in countries whose governments Mr Chávez dislikes.
The countries whose HDI has improved the most since 1980 are mainly in Asia.
The eight EU countries whose leaders were not invited to dinner were furious.
The tax would be split, in normal circumstances, between the countries whose institutions were involved.
