Columbia subject headings:
Geology, Stratigraphic--Ordovician.
Stratigraphic correlation--Asia, Central.
Stratigraphic correlation--Kazakhstan.
Harvard subject headings:
Geology, Stratigraphic--Ordovician
Stratigraphic correlation--Asia, Central.
Stratigraphic correlation--Kazakhstan.
Princeton subject headings:
Geology, Stratigraphic--Ordovician.
Geology--Kazakhstan.