Columbia subject headings:
Harvard subject headings:
Plumbers--Labor unions--North America--Periodicals.
Plumbers--Periodicals.
United Association of Journeymen and Apprentices of the Plumbing and Pipe Fitting Industry--Periodicals.
Princeton subject headings:
Plumbers--Labor unions--North America--Periodicals.
United Association of Journeymen and Apprentices of the Plumbing and Pipe Fitting Industry.