Congresses 285 Economic conditions 196 History 193 Problems, exercises, etc 153 Politics and government 137 Social conditions 133 Economic policy 115 Social problems 101 Education 89 Economic aspects 80 Case studies 72 Economics 70 Philosophy 69 Problem solving 66 Agriculture 61 Data processing 60 Foreign relations 56 Mathematics 55 Accounting 53 Mathematical models 53 Research 47 Finance 45 History and criticism 44 Study and teaching 43 Management 42 Law and legislation 40 Cities and towns 39 City planning 39 Industrial management 36 Boundary value problems 35