  Scaling studies of inclusive quasielastic electron scattering reactions have
been used in the past as a basic tool to obtain information on the nucleon
momentum distribution in nuclei. However, the connection between the scaling
function, extracted from the analysis of cross section data, and the spectral
function only exists assuming very restricted approximations. We revisit the
basic expressions involved in scaling studies and how they can be linked to the
nucleon momentum distribution. In particular, the analysis applied in the past
to the so-called scaling region, {\it i.e.,} negative values of the scaling
variable $y$, is extended here to positive $y$, since a "universal"
superscaling function has been extracted from the analysis of the separated
longitudinal data. This leads to results that clearly differ from the ones
based solely on the negative-$y$ scaling region, providing new information on
how the energy and momentum are distributed in the spectral function.
