Columbia subject headings:
Gardens--Design--Congresses.
Historic gardens--Conservation and restoration--Congresses.
Parks--Congresses.
Harvard subject headings:
Gardens--Design--Congresses.
Historic gardens--Conservation and restoration--Congresses.
Landscape architecture--Congresses
Parks--Congresses.
Princeton subject headings:
Landscape architecture--Congresses.
Monuments--Conservation and restoration--Congresses.