Columbia subject headings:
Harvard subject headings:
National parks and reserves--Europe--History--20th century--Congresses.
National parks and reserves--Europe--History--21st century--Congresses.
National parks and reserves--Italy--History--20th century--Congresses.
National parks and reserves--Italy--History--21st century--Congresses.
Princeton subject headings:
National parks and reserves--Europe--History--20th century--Congresses.
National parks and reserves--Europe--History--21st century--Congresses.
National parks and reserves--Italy--History--20th century--Congresses.
National parks and reserves--Italy--History--21st century--Congresses.