Columbia subject headings:
International Socialist Congress.
Socialism--Congresses.
Socialism.
World War, 1914-1918.
Harvard subject headings:
International Socialist Congress.
Internationale socialist congress.
Socialism
Socialism--Congresses
World War, 1914-1918
Princeton subject headings:
Socialism--Congresses.
Socialism.
Socialist International (1889-1922)
World War, 1914-1918.