Columbia subject headings:
Harvard subject headings:
Environmental protection--Alps--Congresses.
Human ecology--Alps--Congresses.
Landscape changes--Alps--Congresses.
Landscape protection--Alps--Congresses.
Mountain tourism--Environmental aspects--Congresses.
Tourism--Alps--Congresses.
Tourism--Environmental aspects--Alps--Congresses.
Princeton subject headings:
Environmental protection--Alps.
Human ecology--Alps.
Landscape changes--Alps.
Landscape protection--Alps.
Mountain tourism--Environmental aspects.
Tourism--Alps.
Tourism--Environmental aspects--Alps.