Columbia subject headings:
Communism--Congresses.
Partido dos Trabalhadores (Brazil)--Congresses.
Socialism--Congresses.
Harvard subject headings:
Partido dos Trabalhadores (Brazil)--Congresses.
Socialism--Brazil--Congresses.
Princeton subject headings:
Communism--Congresses.
Partido dos Trabalhadores (Brazil)--Congresses.
Socialism--Congresses.