Columbia subject headings:
Geology, Stratigraphic--Permian.
Geology--Europe.
Richter-Bernburg, G.
Harvard subject headings:
Geology, Stratigraphic--Permian
Geology--Europe
Richter-Bernburg, G.
Princeton subject headings:
Geology, Stratigraphic--Permian.
Geology--Europe.
Richter-Bernburg, G.