Columbia subject headings:
Canal Zone--History--Sources.
Panama Canal Treaties
Panama--Foreign relations--United States.
Panama--History--Sources.
United States--Foreign relations--Panama.
Harvard subject headings:
Canal Zone--History.
Panama Canal (Panama)--History.
Panama Canal Treaties--History.
Panama--Foreign relations--United States.
United States--Foreign relations--Panama.
Princeton subject headings:
Canal Zone--History.
Panama Canal (Panama)--History.
Panama Canal Treaties--History.
Panama--Foreign relations--United States.
United States--Foreign relations--Panama.