Columbia subject headings:
Labor laws and legislation--United States.
Labor unions--United States.
Supervisors, Industrial.
United States. National Labor Relations Board.
Harvard subject headings:
Labor laws and legislation--United States
Labor unions--United States
Supervisors, Industrial
United States. National Labor Relations Board
Princeton subject headings:
Labor laws and legislation--United States.
Labor unions--United States.
Supervisors, Industrial.
United States. National Labor Relations Board