Columbia subject headings:
Carcinogens--Congresses.
Petroleum products--Congresses.
Petroleum--Refining--Toxicology--Congresses.
Harvard subject headings:
Carcinogens--Congresses
Carcinogens--Environmental aspects--Congresses.
Petroleum--Refining--Physiological effect--Congresses.
Petroleum--Toxicology--Congresses.
Princeton subject headings: