1. Is volume related to outcome in health care? A systematic review and methodologic critique of the literature;Halm;Ann Intern Med,2002
2. National Hospital Ambulatory Medical Care Survey. Emergency department summary;National Center for Health Statistics (U.S.),2004
3. Overcrowding in the nation's emergency departments: complex causes and disturbing effects;Derlet;Ann Emerg Med,2000
4. Committee on the Future of Emergency Care in the US Health System.: the future of emergency care in the United States health system;Institute of Medicine (U.S.),2006
5. Chronic obstructive pulmonary disease surveillance—United States, 1971-2000;Mannino;MMWR Surveill Summ,2002