Columbia subject headings:
Carriers--United States--Statistics--Periodicals.
Telecommunication--United States--Statistics--Periodicals.
Harvard subject headings:
Carriers--United States--Statistics--Periodicals.
Periodicals
Statistics
Telecommunication--United States--Statistics--Periodicals.
Princeton subject headings:
Carriers--United States--Statistics--Periodicals.
Periodicals.
Statistics.
Telecommunication--United States--Statistics--Periodicals.