Columbia subject headings:
Interstellar matter--Congresses.
Polycyclic aromatic hydrocarbons--Congresses.
Harvard subject headings:
Interstellar matter--Congresses.
Polycyclic aromatic hydrocarbons--Congresses.
Princeton subject headings:
Interstellar matter--Congresses.
Polycyclic aromatic hydrocarbons--Congresses.