Dilemmas in counting the homeless: introduction.
D003430:Cross-Sectional Studies; D003710:Demography; D006703:Ill-Housed Persons / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D014481:United States / Q000453:epidemiology; D014505:Urban Population / Q000706:statistics & numerical data*