Columbia subject headings:
Harvard subject headings:
Energy consumption--Germany--North Rhine-Westphalia.
Energy policy--Germany--North Rhine-Westphalia.
Power resources--Germany--North Rhine-Westphalia.
Renewable energy sources--Government policy--Germany--North Rhine-Westphalia.
Solar energy--Germany--North Rhine-Westphalia.
Princeton subject headings:
Energy consumption--Germany--North Rhine-Westphalia.
Energy policy--Germany--North Rhine-Westphalia.
Power resources--Germany--North Rhine-Westphalia.
Renewable energy sources--Government policy--Germany--North Rhine-Westphalia.
Solar energy--Germany--North Rhine-Westphalia.