Energy conservation 9 Agricultural conservation 8 Conservation and restoration 3 Conservation and restoration. Preservation and restoration of architectural monuments 3 Historic buildings 3 Natural History Including nature conservation, geographical distribution 3 Soil conservation and protection 3 Soils. Soil science. Including soil surveys, soil chemistry, soil structure, soil-plant relationships 3 Agricultural ecology (General) 2 Agriculture and the environment 2 Agroforestry 2 Fertilizers and improvement of the soil 2 Mechanics applied to machinery. Dynamics 2 Museums. Exhibitions 2 NA Architecture 2 Villages 2 Administration. Policy 1 Analytical methods used in the solution of physical problems 1 City planning. Regional planning 1 Conservation and restoration of drawings 1 Distillation 1 Ecology 1 Energy consumption 1 Environmental protection 1 Farmers 1 Fisheries 1 General. Including nature conservation, geographical distribution 1 Geographic information systems 1 Heat engines 1 Heat. Heat in its applications, as a source of power, etc 1