Columbia subject headings:
Canon law--History--12th century.
Canon law--History.
Church and state--History--12th century.
Church and state--History.
Placidus, active 12th century. De honore ecclesiae.
Placidus, of Nonantola, active 12th century. De honore Ecclesiae.
Harvard subject headings:
Canon law--History.
Church and state--History
Placidus, 12th century. Liber de honore ecclesiae.
Princeton subject headings:
Canon law--History--12th century.
Church and state--History--12th century.
Placidus, 12th century. Liber de honore ecclesiae.