1. McNish, A. G., , “Terrestrial Magnetism and Electricity”, J. A., Fleming, , 308-359 McGraw-Hill, New York, 1939,
2. Chapman, S., , “The Earth's Magnetism,”, Methuen and Co., Ltd., London, 1936,
3. Chapman, S., , J., BaFeels, , “Geomagnetism,”, Clarendon Press, Oxford, 1940,
4. Bauer, L. A., , , Terr. Mag., , 25, , 145– -162 ( 1920, ); 28, 1–28 (1923).
5. Stewart, B., , Ency. Britt, , 16, 9th ed. 181-184 1882,