Agriculture 2,477 Economic aspects 1,188 Agriculture and state 445 History 386 Periodicals 216 Agricultural laborers 194 Research 189 Congresses 169 Economic conditions 156 Rural conditions 153 Land tenure 148 Food supply 125 Agriculture, Cooperative 105 Agricultural machinery 87 Produce trade 71 Agricultural extension work 68 Rural development 65 Land reform 64 Agricultural industries 60 Statistics 60 Peasantry 59 Agricultural credit 57 Case studies 57 Agricultural education 56 Agricultural engineering 55 Experimentation 54 Agricultural innovations 47 Economic policy 45 Land use 45 Farm management 44