Columbia subject headings:
Harvard subject headings:
Portugal--History--Period of discoveries, 1385-1580.
Science and civilization--History--15th century.
Science and civilization--History--16th century.
Science--Portugal--History--15th century.
Science--Portugal--History--16th century.
Princeton subject headings:
Portugal--History--Period of discoveries, 1385-1580.
Science and civilization--History.
Science--Portugal--History.