Columbia subject headings:
Europe--Foreign relations--United States.
National security--United States.
North Atlantic Treaty Organization--Membership.
United States--Foreign relations--Europe.
United States--Military policy.
Harvard subject headings:
Europe--Foreign relations--United States.
National security--United States
North Atlantic Treaty Organization--Membership.
United States--Foreign relations--Europe.
United States--Military policy.
Princeton subject headings:
Europe--Foreign relations--United States.
National security--United States.
North Atlantic Treaty Organization--Membership.
United States--Foreign relations--Europe.
United States--Military policy.