The temperature dependence of the viscosity of inorganic glasses in the glass transition region is successfully described by the Williams--Landel--Ferry (WLF) equation. For the studied glasses, the value of f_g=1/C1 weakly depends on the nature of the glasses. There is a linear correlation between delta delta Tg and Tg. From the data on the parameters of the WLF equation C1 and C2, we calculated delta delta Tg, as well as the relaxation time of the structure taug at the glass transition temperature of the glasses under study. Keywords: Viscosity in the glass transition region, Williams--Landel--Ferry equation, kinetic glass transition criterion, chalcogenide glasses, fluctuation volume fraction, liquid--glass transition.