Columbia subject headings:
Labor bureaus--United States.
Labor bureaus.
Working class--Statistics.
Working class--United States--Statistics.
Harvard subject headings:
Labor bureaus--United States.
Labor bureaus.
Labor--United States--Statistics.
Working class--Statistics
Working class--United States--Statistics.
Princeton subject headings:
Labor bureaus--United States.
Labor bureaus.
Statistics.
Working class--Statistics.
Working class--United States--Statistics.