9 Botany 9 Natural history 6 Paleontology 5 Antiquities 5 Zoology 4 Stone age 3 Civilization 3 Ecology 3 Forests and forestry 3 Natural resources 3 Scientific expeditions 3 Steppes 2 Archaeological expeditions 2 Description and travel 2 Desert ecology 2 Earthquakes 2 Fishes 2 Geology 2 Pastures 2 Physical geography 2 Soils 2 Time management 1 Amphibians 1 Arts 1 Biosphere 1 Biotic communities 1 Classification 1 Collected works 1 Congresses 1 Conservation of natural resources