Columbia subject headings:
Mass media--United States.
Monopolies--United States.
Press monopolies--United States.
Press--United States.
Harvard subject headings:
Mass media--United States
Monopolies--United States.
Press monopolies--United States.
Press--United States
Princeton subject headings:
Mass media--United States.
Monopolies--United States.
Press monopolies--United States.
Press--United States.