Columbia subject headings:
Harvard subject headings:
Astronomers--Denmark--Biography.
Astronomers--Germany--Biography
Astronomy--History
Brahe, Tycho, 1546-1601
Kepler, Johannes, 1571-1630
Mathematicians--Germany--Biography
Reimers Ursus, Nicholas, 1551-1600
Princeton subject headings:
Astronomers--Denmark--Biography.
Astronomers--Germany--Biography.
Astronomy--History.
Brahe, Tycho, 1546-1601.
Kepler, Johannes, 1571-1630.
Mathematicians--Germany--Biography.
Reimers Ursus, Nicholas, 1551-1600.