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Subject
- Geology[remove]615
- Geology, Stratigraphic240
- Paleontology41
- Mines and mineral resources32
- Petrology22
- Physical geography17
- Groundwater13
- Water-supply13
- Petroleum11
- Mineralogy9
- Phosphates9
- Earth sciences8
- Ore deposits8
- Geochemistry7
- Geological Survey (U.S.)7
- Paleogeography7
- Glacial epoch6
- Gold ores6
- Phosphate rock6
- Prehistoric peoples6