Congresses 224 Economic conditions 129 Politics and government 78 Economic policy 73 History 70 Education 69 Economic aspects 67 Regional planning 66 Social aspects 65 Foreign exchange futures 61 City planning 57 Land use 56 Forecasting 49 Research 47 Social conditions 42 Study and teaching 38 Management 37 Accounting 36 Education, Higher 33 Power resources 32 Cities and towns 31 Environmental policy 31 Mathematical models 31 Technology 31 Energy policy 30 Environmental aspects 30 Agriculture 29 Natural resources 29 Planning 28 Technological innovations 28