Columbia subject headings:
Europe, Eastern--Defenses.
National security--Europe.
North Atlantic Treaty Organization--Europe, Eastern.
North Atlantic Treaty Organization--Membership.
Harvard subject headings:
Europe, Eastern--Defenses.
National security--Europe
North Atlantic Treaty Organization--Europe, Eastern.
North Atlantic Treaty Organization--Membership.
Princeton subject headings:
Europe, Eastern--Defenses.
National security--Europe.
North Atlantic Treaty Organization--Europe, Eastern.
North Atlantic Treaty Organization--Membership.