Education 38 History 36 Social aspects 34 Study and teaching 31 Addresses, essays, lectures 28 Underdeveloped areas 26 Management 24 Data processing 23 Materials 20 Planning 17 Regional planning 17 Science 17 City planning 16 Technological innovations 16 Economic aspects 15 Social conditions 15 International economic relations 14 Mathematical models 14 Politics and government 14 Research 14 Chemical engineering 13 Economic conditions 13 Metals 13 Technology 13 Geology 11 Analysis 10 Cities and towns 10 English language 10 Fluid dynamics 10 Foreign relations 10