Columbia subject headings:
Harvard subject headings:
Slopes (Physical geography)--Congresses.
Slopes (Physical geography)--Rocky Mountains--Congresses.
Slopes (Physical geography)--West (U.S.)--Congresses.
Princeton subject headings:
Slopes (Physical geography)--Congresses.
Slopes (Physical geography)--Rocky Mountains--Congresses.
Slopes (Physical geography)--West (U.S.)--Congresses.