Columbia subject headings:
Antipopes--History--Congresses.
Church history--Middle Ages, 600-1500--Congresses.
Papacy--History--Congresses.
Harvard subject headings:
Antipopes--History--Congresses.
Church history--Middle Ages, 600-1500--Congresses.
Conference papers and proceedings.
Papacy--History--Congresses.
Princeton subject headings: