1. Howe , H. H. E. K. Weisman Geomagnetic indices K and C , 1948 12b Association of Terrestrial Magnetion and Electricity, International Union Geodesy and Geophysics Washington, D. C. 1949
2. Johnston , H. F. W. E. Scott E. Balsam Geomagnetic indices C and K , 1940-1946 12 Association of Terrestrial Magnetism and Electricity, International Union Geodesy and Geophysics Washington, D. C. 1948
3. Rapports scientifiques des Expeditions Polaires Francaises S IV 2;Mayaud;Ann. geophys.,1956
4. On the annual variation of magnetic disturbance;McIntosh;Phil. Trans. Roy. Soc. London, A,1959
5. The diurnal variation of irregular geomagnetic fluctuations;Nicholson;J. Geophys. Research,1955