(1) THE theory of maxima and minima contains pitfalls into which have fallen such well-known mathematicians as Lagrange, Bertrand, Serret, and Todhunter. A peculiar interest, therefore, is attached to ...

In this study, we compared the modelled total electron content (TEC), i.e. ionospheric TEC derived from the latest International Reference Ionosphere (IRI) versions (viz. IRI-2007, IRI-2012 and ...