Columbia subject headings:
Mouth--Cancer--Etiology.
Mouth--Diseases--Etiology.
Smokeless tobacco--Toxicology--United States.
Tobacco use--United States.
Harvard subject headings:
Mouth--Cancer--Etiology
Mouth--Diseases--Etiology.
Smokeless tobacco--Toxicology--United States.
Tobacco use--United States
Princeton subject headings:
Mouth--Cancer--Etiology.
Mouth--Diseases--Etiology.
Smokeless tobacco--Physiological effect.
Smokeless tobacco--Toxicology--United States.
Tobacco use--United States.