Columbia subject headings:
Harvard subject headings:
Energy conservation--European Union countries--Technological innovations.
Renewable energy sources--European Union countries--Technological innovations.
Renewable energy sources--Research--European Union countries .
Renewable natural resources--Research--European Union countries.
Princeton subject headings:
Energy conservation--European Union countries--Technological innovations.
Renewable energy sources--European Union countries--Technological innovations.
Renewable energy sources--Research--European Union countries.
Renewable natural resources--Research--European Union countries.