title: Primary care and emergency department overcrowding. 1. Achieving proportionate representation in samples.
authors.forename: R
authors.initials: R
authors.lastname: Ullman
authors.forename: W C
authors.initials: WC
authors.lastname: Stratmann
mesh_terms: D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D006801:Humans; D011320:Primary Health Care / Q000706:statistics & numerical data; D015983:Selection Bias; D014481:United States