Columbia subject headings:
Geology, Stratigraphic--Cambrian.
Geology, Stratigraphic--Precambrian.
Paleontology--Cambrian.
Paleontology--Precambrian.
Harvard subject headings:
Princeton subject headings:
Geology, Stratigraphic--Cambrian.
Geology, Stratigraphic--Precambrian.
Paleontology--Cambrian.
Paleontology--Precambrian.