Columbia subject headings:
Comets--Congresses.
Halley's comet--Congresses.
Space plasmas--Congresses.
Harvard subject headings:
Comets--Congresses
Halley's comet--Congresses.
Space plasmas--Congresses.
Princeton subject headings:
Comets--Congresses.
Halley's comet--Congresses.
Space plasmas--Congresses.