Geology 678 History 256 Historical geography 169 Geology, Structural 100 Maps 95 Administrative and political divisions 92 Geology, Stratigraphic 83 more ... Mines and mineral resources 82 Population 80 Groundwater 71 Aquifers 65 Publications by Graduates 58 Outdoor recreation 57 Atlases 49 Economic conditions 49 Census districts 48 Water table 40 Hydrogeology 37 Housing 36 Cartography 32 Geochemical prospecting 31 Ocean bottom 28 Social conditions 28 Gravity anomalies 27 Physical geography 27 Submarine topography 25 National parks and reserves 24 Sediments (Geology) 24 Campaigns 23 Geography 23 less ...