Columbia subject headings:
International Workingmen's Association--History--Sources--Bibliography--Catalogs.
Socialism--Belgium--History--Sources--Bibliography--Catalogs.
Harvard subject headings:
International Workingmen's Association--History--Sources--Bibliography--Catalogs.
Socialism--Belgium--History--Sources--Bibliography--Catalogs.
Socialism--Belgium--Sources--Bibliography--Catalogs.
Princeton subject headings:
International Workingman's Association--History--Sources.
Socialists--Belgium--Correspondence.
Working class--Belgium--Political activity--History--Sources.