Columbia subject headings:
Harvard subject headings:
Geology, Economic--Williston Basin--Congresses.
Geology, Stratigraphic--Congresses
Geology--Williston Basin--Congresses.
Petroleum--Geology--Williston Basin--Congresses.
Williston Basin--Congresses.
Princeton subject headings:
Geology--North Dakota--Congresses.
Geology--Williston Basin--Congresses.