Columbia subject headings:
Journalism--Social aspects--United States.
News agencies--Social aspects--United States.
Postal service--United States--History.
Postal service--United States--Second-class matter--History.
Harvard subject headings:
Journalism--Social aspects--United States.
News agencies--Social aspects--United States.
Postal service--United States--History
Postal service--United States--Second-class matter--History.
Princeton subject headings:
News agencies--United States--Social aspects.
Postal service--United States--History.
Postal service--United States--Second-class matter--History.
Press--Social aspects--United States.