1. Arkani-Hamed, J., R. A. Langel, and M. Purucker, Magnetic anomaly maps of the Earth derived from POGO and Magsat data, J. Geophys. Res., 99, 24075–24090, 1994.
2. Backus, G., R. Parker, and C. Constable, Foundations of Geomagnetism, p. 140, Cambridge University Press, 1996.
3. Cain, J. C., Z. Wang, C. Kluth, and D. R. Schmitz, Derivation of a geomag netic model to n = 63, Geophys. J. Int., 97, 43–441, 1989.
4. Kaiser, J. F., Nonrecursive digital filter design using window function, in Proceedings of the 1974 IEEE International Symposium on Circuits and Systems, pp. 20–23, IEEE, New York, 1974.
5. Langel, R. A. and W.J. Hinze, The Magnetic Field of the Earth’s Lithosphere, 429 pp., Cambridge University Press, 1998.