Columbia subject headings:
Labor movement--Italy--Congresses.
Trentin, Bruno--Congresses.
Harvard subject headings:
Communists--Italy--Biography--Congresses.
Labor leaders--Italy--Biography--Congresses.
Law--Interpretation and construction
Legal certainty.
Trentin, Bruno--Congresses.
Princeton subject headings:
Labor movement--Italy--Congresses.
Trentin, Bruno--Congresses.