  Glassy behavior is a generic feature of electrons close to disorder-driven
metal-insulator transitions. Deep in the insulating phase, electrons are
tightly bound to impurities, and thus classical models for electron glasses
have long been used. As the metallic phase is approached, quantum fluctuations
become more important, as they control the electronic mobility. In this paper
we review recent work that used extended dynamical mean-field approaches to
discuss the influence of such quantum fluctuations on the glassy behavior of
electrons, and examine how the stability of the glassy phase is affected by the
Anderson and the Mott mechanisms of localization.
