Subject
- Boundaries40
- Geoscientific Information40
- Environment36
- Oceans33
- Transportation23
- Economy21
- Society20
- Inland Waters14
- Administrative and political divisions13
- Biology and Ecology10
- Counties10
- Geomagnetism10
- Utilities and Communication10
- Minerals9
- Mines and mineral resources9
- Location8
- Planning and Cadastral8
- Structure8
- States7
- Drainage6