Columbia subject headings:
Harvard subject headings:
Geology, Stratigraphic--Carboniferous--Congresses
Geology--Europe--Congresses
Paleontology--Carboniferous--Congresses.
Princeton subject headings:
Geology, Stratigraphic--Carboniferous--Congresses.
Geology--Europe--Congresses.
Paleontology--Carboniferous--Congresses.