Columbia subject headings:
International and municipal law--Europe--Congresses.
Harvard subject headings:
Customary law, International--Congresses.
International and municipal law--Europe--Congresses.
International law--Poland--Congresses.
Law--Europe--International unification--Congresses.
Law--Poland--Congresses.
Sovereignty--Congresses.
Princeton subject headings:
International and municipal law--Europe--Congresses.