Rules and practice 6,612 Renewable energy sources 1,188 Robotics 712 Racism 569 Reorganization 562 Research 562 Religion 556 Roads 493 Risk management 451 Recreation areas 411 Refuse and refuse disposal 400 Runoff 360 Rivers 355 Restoration ecology 340 Russia (Federation) Foreign relations 339 Rural development 332 Recruiting 328 River sediments 317 R (Computer program language) 307 Reading 306 Regional planning 301 Recycling (Waste, etc.) 293 Remote sensing 290 Rome History 282 Radioactive waste disposal in the ground 273 Religions 273 Renaissance 268 Relationship quality 263 Radioactive waste disposal 257 Romanticism 249 Range management 242 Risk assessment 238 Refugees 233 Religion and sociology 226 Reservoirs 223 Radioactive substances 219 Reading (Elementary) 219 Research Law and legislation 210 River channels 206 Reclamation of land 199 Reformation 198 Reliability (Engineering) 197 Real property 196 Respiratory organs Diseases 196 Race discrimination 192 Railroads 190 Radioactive prospecting 187 Reproduction 187 Reservoir sedimentation 182 Roads Design and construction 181 Religious institutions 180 Research grants 179 Rock mechanics 178 Retirement income 176 Rain and rainfall 174 Rocks Analysis 172 Representative government and representation 171 Regenerative medicine 169 Reconstruction (1939-1951) 167 Race relations 165 Renewable energy sources Law and legislation 159 Real property, Exchange of 157 Reading comprehension 155 Russia History 155 Recruiting, enlistment, etc 154 Rock music 154 Revolutions 153 Ritual 153 Relativity (Physics) 151 Regression analysis 148 Radicalism 146 Retail trade 146 Report writing 145 Reproductive health 144 Rites and ceremonies 144 Radiology 143 Reasoning 143 Research and development contracts, Government 140 Roads Finance 137 Robots 136 Rural health services 135 Renewable energy sources Government policy 134 Reconstruction (U.S. history, 1865-1877) 132 Religion Philosophy 130 Robots Control systems 130 Riparian ecology 125 Rare earths 124 Regional economics 124 Right of property 123 Rape 122 Referendum 122 Relational databases 122 Roads Design and construction Environmental aspects 120 Recidivism Prevention 119 Reading (Primary) 118 Refugees Government policy 117 Rural development Appropriations and expenditures 116 Ranch life 115 Russia (Federation) History 114 Real property tax 113