Columbia subject headings:
Harvard subject headings:
Gauss, Carl Friedrich, 1777-1855--Correspondence.
Geomagnetism--Germany--History--Sources.
Kreil, Karl, 1798-1862--Correspondence.
Princeton subject headings:
Gauss, Carl Friedrich, 1777-1855--Correspondence.
Geomagnetism--Germany--History--Sources.
Kreil, Karl, 1798-1862--Correspondence.