title: Variations in primary medical care: influence of health plans and practice organizations.
authors.forename: E C
authors.initials: EC
authors.lastname: Rich
mesh_terms: D005245:Fee Schedules; D008329:Managed Care Programs / Q000191:economics / Q000458:organization & administration; D006278:Medicare / Q000191:economics; D010818:Practice Patterns, Physicians'; D011320:Primary Health Care / Q000191:economics / Q000458:organization & administration*; D014481:United States