Columbia subject headings:
Grétry, André-Ernest-Modeste, 1741-1813.
Harvard subject headings:
Grétry, André-Ernest-Modeste, 1741-1813--Congresses.
Opera--Europe--Congresses.
Princeton subject headings:
Grétry, André-Ernest-Modeste, 1741-1813--Congresses.
Opera--France--18th century--Congresses.