Columbia subject headings:
Geology--Missouri River Valley.
Geology--Yellowstone River Valley.
Paleobotany--Cretaceous Tertiary.
Harvard subject headings:
Geology--Missouri River Valley.
Geology--Yellowstone River Valley.
Paleobotany--Missouri River Valley.
Paleobotany--Yellowstone River Valley.
Princeton subject headings:
Geology--Missouri River Valley.
Geology--Yellowstone River Valley.
Paleobotany--Missouri River Valley.
Paleobotany--Yellowstone River Valley.