Columbia subject headings:
Harvard subject headings:
Energy policy--European Union countries
Energy policy--Germany
Energy policy--Poland.
Europe--Economic integration.
Renewable energy sources--European Union countries.
Renewable energy sources--Germany.
Renewable energy sources--Poland.
Princeton subject headings:
Energy policy--European Union countries.
Energy policy--Germany.
Energy policy--Poland.
Europe--Economic integration.
Renewable energy sources--Germany.
Renewable energy sources--Poland.