Columbia subject headings:
Harvard subject headings:
Germany--Politics and government--Congresses.
Oertzen, Peter von--Congresses.
Political parties--Germany--Congresses.
Socialism and education--Germany--Congresses.
Socialism--Germany--Congresses.
Sozialdemokratische Partei Deutschlands--Congresses.
Princeton subject headings:
Oertzen, Peter von--Political and social views.
Oertzen, Peter von.
Political scientists--Germany--Biography.
Socialists--Germany--Biography.