Columbia subject headings:
Harvard subject headings:
Geology, Stratigraphic--Ordovician
Geology, Stratigraphic--Russia (Federation)--Siberia.
Paleontology--Ordovician
Paleontology--Russia (Federation)--Siberia
Princeton subject headings:
Geology, Stratigraphic--Ordovician.
Geology--Russia (Federation)--Lena River Watershed.
Paleontology--Ordovician.
Paleontology--Russia (Federation)--Lena River Watershed.