Population density and the city.
D000818:Animals; D002958:City Planning; D003142:Communication; D003163:Competitive Behavior; D003365:Costs and Cost Analysis; D003441:Crowding; D004781:Environmental Exposure; D005060:Europe; D049672:History, 19th Century; D049673:History, 20th Century; D006801:Humans; D007221:Industry; D009017:Morbidity; D009026:Mortality; D009934:Organization and Administration; D011156:Population Density; D011157:Population Dynamics; D011158:Population Growth; D051381:Rats; D012940:Social Problems; D014481:United States; D014505:Urban Population; D014507:Urbanization / Q000266:history