Medicare HMOs: fix Medicare first.
D000368:Aged; D003191:Comprehensive Health Care / Q000191:economics; D003284:Contract Services / Q000191:economics*; D005376:Financial Management / Q000191:economics*; D006279:Health Maintenance Organizations / Q000191:economics*; D006801:Humans; D006278:Medicare / Q000458:organization & administration*; D008962:Models, Theoretical; D012306:Risk; D012495:San Francisco; D014481:United States