Columbia subject headings:
Geology, Stratigraphic--Precambrian--Congresses.
Geology--Rocky Mountains Region--Congresses.
Harvard subject headings:
Geology, Stratigraphic--Precambrian--Congresses
Geology--Rocky Mountains Region--Congresses.
Princeton subject headings:
Geology, Stratigraphic--Precambrian--Congresses.
Geology--Rocky Mountains Region--Congresses.