Lastovicka, J., P. Sauli, and P. Krizan. “Persistence of Planetary Wave Type Oscillations in the Mid-Latitude Ionosphere”. Annals of Geophysics 49, no. 6 (December 25, 2006). Accessed May 13, 2026. https://www.annalsofgeophysics.eu/index.php/annals/article/view/3098.