On a predominant ionization source in the main maximum of the Venus nightside ionosphere

New considerations in favour of the previously made hypothesis, made on the basis of data using ''Venera-9 and 10'' satellites, that electron fluxes are the main ionization sources, creating the upper maximum of electron concentration in the night Venus atmosphere, are presented. Analysis of arguments, made by certain american authors, suggesting that O+ ion transfer from the day Venus ionosphere to the night one should be considered as the main source of night ionization is made, and inconsistency of the argument shown