HMOs: origins and development.
D006125:Group Practice, Prepaid / Q000266:history; D006279:Health Maintenance Organizations / Q000266:history* / Q000331:legislation & jurisprudence; D006291:Health Policy / Q000266:history; D049673:History, 20th Century; D009786:Occupational Health Services / Q000266:history; D011057:Politics; D012955:Societies, Medical / Q000266:history; D014481:United States