Physicians. Look for the union label.
Meyer
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D016363:Antitrust Laws; D003098:Collective Bargaining / Q000331:legislation & jurisprudence; D007750:Labor Unions / Q000331:legislation & jurisprudence*; D010820:Physicians / Q000331:legislation & jurisprudence*; D014481:United States; D014485:United States Federal Trade Commission