HMOs and PPOs: similarities and differences.
D006279:Health Maintenance Organizations / Q000191:economics / Q000458:organization & administration; D007348:Insurance, Health / Q000191:economics / Q000458:organization & administration; D007349:Insurance, Health, Reimbursement; D008962:Models, Theoretical; D011243:Preferred Provider Organizations / Q000191:economics / Q000458:organization & administration; D014481:United States