1,278 History 1,121 Geology 689 Geology, Stratigraphic 535 Antiquities 453 Economic conditions 343 Research 342 Politics and government 301 Paleontology 297 Ore deposits 270 Petrology 269 Ethnology 258 Soils 249 Economic policy 244 Botany 237 Excavations (Archaeology) 226 Social conditions 210 Economic aspects 205 Social life and customs 200 Petroleum 199 Ecology 195 Geology, Structural 182 Forests and forestry 175 Agriculture 155 Environmental aspects 146 Mineralogy 146 Natural gas 144 Natural resources 142 Nationalism 140 Mines and mineral resources 132 Mathematical models