Current density functional theory in the age of generalized Kohn-Sham theories

I review the evolution of electronic non-relativistic current density functional theory (CDFT) from its original formulation in the late 1980's to present day's formulations, which rely on the generalized Kohn-Sham theory. Axel Becke's outstanding contributions are highlighted throughout. I propose a form of the generalized Kohn-Sham equation that combines the exchange-correlation vector potential of the original formulation with an "effective mass term" -the latter following from the inclusion of Becke's kinetic energy density as a basic input of the exchange-correlation energy functional.