  A new technique was recently developed to approximate the solution of the
Schroedinger equation. This approximation (dubbed ERS) is shown to yield a
better accuracy than the WKB-approximation. Here, we review the ERS
approximation and its application to one and three-dimensional systems. In
particular, we treat bound state solutions. We further focus on random
potentials in a quantum wire and discuss the solution in the context of
Anderson localization.
