Columbia subject headings:
Cardinals--Biography.
Clement VIII, Pope, 1536-1605.
Gregory XIV, Pope, 1535-1591.
Italy--Description and travel--Early works to 1800.
Popes--Biography.
Sixtus V, Pope, 1520-1590.
Tofte, Robert, 1561-1620. Discourse of the five last popes of Rome.
Harvard subject headings:
Cardinals--Biography--Early works to 1800.
Catholic Church--History--16th century--Sources.
Catholic Church--Italy--Rome--History--Sources.
Popes--Biography--Early works to 1800.
Princeton subject headings:
Cardinals--Biography--Early works to 1800.
Italy--Description and travel--Early works to 1800.
Popes--Biography--Early works to 1800.