R.T. Merrill, M.W. McElhinny: The Earth's Magnetic Field – Its History, Origin and Planetary Perspective. Academic Press Inc., London 1983, ISBN 0-12-491240-0, S. 16 (Google Books)
R.T. Merrill, M.W. McElhinny: The Earth's Magnetic Field – Its History, Origin and Planetary Perspective. Academic Press Inc., London 1983, ISBN 0-12-491240-0, S. 7 (Google Books)