Columbia subject headings:
Professional associations--United States--History.
Trade associations--United States--History.
Trade associations.
Trusts, Industrial--United States--History.
United States. National Recovery Administration.
Harvard subject headings:
Professional associations--United States--History.
Trade associations--United States--History.
Trusts, Industrial--United States--History.
United States. National Recovery Administration
Princeton subject headings:
Trade and professional associations--United States--History.
Trusts, Industrial--United States--History.
United States. National Recovery Administration