Columbia subject headings:
Harvard subject headings:
Geology, Stratigraphic--Pleistocene
Geology, Stratigraphic--Pleistocene--Bibliography.
Geology--Iowa
Geology--Iowa--Bibliography.
Princeton subject headings:
Geology, Stratigraphic--Pleistocene--Bibliography.
Geology, Stratigraphic--Pleistocene.
Geology--Iowa--Bibliography.
Geology--Iowa.