Columbia subject headings:
Harvard subject headings:
Citrus fruits in art--Congresses.
Citrus fruits in literature--Congresses.
Citrus fruits--History--Congresses.
Citrus fruits--Italy--History--Congresses.
Gardens--History--Congresses.
Gardens--Italy--History--Congresses.
Princeton subject headings:
Citrus fruits in art--Congresses.
Citrus fruits in literature--Congresses.
Citrus fruits--History--Congresses.