Columbia subject headings:
Building trades--New York (State)--Nassau County.
Labor unions--New State--Nassau County.
Open and closed shop.
Harvard subject headings:
Building trades--New York (State)--Nassau County.
Labor turnover--New York (State)--Nassau County.
Open and closed shop--New York (State)--Nassau County.
Princeton subject headings:
Building trades--New York (State)--Nassau County.
Labor turnover--New York (State)--Nassau County.
Open and closed shop--New York (State)--Nassau County.