Close Diurnal Variation of the Total Electron Content under Quiet Helio-Geomagnetic Conditions,
Perevalova, N. P., A. S. Polyakova, A. V. Zalizovski (2010),
Journal of Atmospheric and Solar-Terrestrial Physics, 72 p. 997–1007,
10.1016/j.jastp.2010.05.014.