Subject
- Lutheran Church1
- Metropolitan areas1
- Mountain passes1
- Natural gas1
- Oats1
- Occupied territories1
- Ocean currents1
- Oceanography1
- Ore deposits1
- Ouvrages anciens, jusqu'à 16001
- Paraguayan War, 1865-18701
- Petroleum1
- Petroleum industry and trade1
- Pneumatic-tube transportation1
- Politics and government1
- Prussia, East (Poland and Russia)1
- Radio stations1
- Religion1
- Romanian language1
- Russian1
