Columbia subject headings:
Holy Roman Empire--History--1273-1517--Sources.
Holy Roman Empire--History--Interregnum, 1254-1273--Sources.
Harvard subject headings:
Holy Roman Empire--History--1273-1517--Sources.
Holy Roman Empire--History--Interregnum, 1254-1273--Sources.
Princeton subject headings:
Constitutional history--Germany--Sources.
Constitutional history--Holy Roman Empire--Sources.