Columbia subject headings:
Organ (Musical instrument)--Germany (East)--Congresses.
Organ (Musical instrument)--Poland--Congresses.
Organ music--History and criticism--Congresses.
Harvard subject headings:
Organ (Musical instrument)--Germany--Congresses.
Organ (Musical instrument)--Poland--Congresses.
Organ music--Congresses.
Princeton subject headings:
Organ (Musical instrument)--Germany (East)--Congresses.
Organ (Musical instrument)--Poland--Congresses.
Organ music--History and criticism--Congresses.