Columbia subject headings:
Harvard subject headings:
Papal States--Economic conditions.
Papal States--History.
Papal States--Social conditions.
Terracina (Italy)--History.
Princeton subject headings:
Marshes--Italy--Pontine Marshes--History--16th century.
Pontine Marshes (Italy)--History--16th century.
Reclamation of land--Italy--Pontine Marshes--History--16th century.
Sixtus V, Pope, 1520-1590.