  It is shown that the latest results from the NMC (CERN) and E665 (Fermilab)
groups on $F_2^A(x)/F_2^D(x)$ obtained in the shadowing region bring new
evidence of the universal $A$ dependence of distortions made in a free-nucleon
structure function by a nuclear medium.
  The observed universality implies that one can consider separately hard
($A\leq$ 4) and soft ($A>$ 4) parton distribution distortions. Soft
distortions, which result in differencies between the deep-inelastic scattering
cross-sections for nuclei with masses $A_1$, $A_2 \geq$ 4, can be explained as
a consequence of the nuclear density variation, independent of $x$ in the range
0.001 $\leq x \leq$ 0.7.
  It is found that nuclear shadowing begins at $x_{\rm I}$ = 0.0615 $\pm$
0.0024, independent of $A$, which is consistent with models that allow for
three-parton recombination processes.

High Energy Physics - Phenomenology