Columbia subject headings:
Harvard subject headings:
Diplomatic and consular service, American--Italy--Papal States.
Diplomatic and consular service, Papal States--United States.
Papal States--Foreign relations--United States.
United States--Foreign relations--Italy--Papal States.
Princeton subject headings:
Diplomatic and consular service, American--Italy--Papal States.
Diplomatic and consular service, Papal States--United States.
Papal States--Foreign relations--United States.
United States--Foreign relations--Italy--Papal States.