Columbia subject headings:
Graptolites--Congresses.
Paleobiology--Congresses.
Paleontology, Stratigraphic--Congresses.
Harvard subject headings:
Graptolites--Congresses.
Graptolites.
Princeton subject headings:
Graptolites--Congresses.
Paleobiology--Congresses.
Paleontology, Stratigraphic--Congresses.