Columbia subject headings:
Harvard subject headings:
Exhibitions--France--Paris--History--19th century--Congresses.
Exhibitions--Portugal--Porto--History--19th century--Congresses.
Gardens--France--Paris--Congresses.
Gardens--Portugal--Porto--Congresses.
Landscape architecture--France--Paris--Congresses.
Landscape architecture--Portugal--Porto--Congresses.
Princeton subject headings:
Exhibitions--France--Paris--History--19th century--Congresses.
Exhibitions--Portugal--Porto--History--19th century--Congresses.
Gardens--France--Paris--Congresses.
Gardens--Portugal--Porto--Congresses.
Landscape architecture--France--Paris--Congresses.
Landscape architecture--Portugal--Porto--Congresses.