1. Hutton , V. R. S. 1959 Diurnal variation of Pc in Ghana, IAGA Bull. 16c 171 172 Proceedings of the Symposium on Rapid Magnetic Variations Utrecht 1959
2. Rivers , D. G. 1967 Observations and analysis of geomagnetic field variations near the magnetic equator Freetown
3. Statistical studies on three types of geomagnetic continuous pulsations, 1, Type I Pc (5-40 sec);Saito;Sci. Rept. Tohoku Univ., ser. 5, Geophys.,1962
4. Seasonal distribution of geomagnetic pulsations;Verö;J. Geophys. Res.,1965