Measurement and Comparison of Total Electron Content for Assessment of Ionospheric Models during April 7, 2000 Geomagnetic Storms oleh Y. O. Kayode, A. S. Ajose, E. O. Onori, A. J. Alomaja, P. C. Offor, S. A. Okedeyi, F. E. Ikuemonisan, A. O. Fakunle, A. R. Adeniji-Adele, R. B. Adegbola