Columbia subject headings:
Crime--United States.
Criminals--United States.
Firearms--Law and legislation--United States.
Harvard subject headings:
Crime--Research--United States.
Crime--United States
Firearms ownership--United States
Firearms--Law and legislation--United States
Gun control--United States
Violent crimes--United States
Princeton subject headings:
Firearms and crime--United States.
Gun control--United States.
Violent crimes--United States.