  Nuclear deep inelastic scattering is considered in the framework of a model
in which the current operator explicitly satisfies Poincare invariance and
current conservation. The results considerably differ from the standard ones at
small values of the Bjorken variable $x$. In particular, it is impossible to
extract the neutron structure functions from the deuteron data at x<0.01 and we
predict that the behavior of the deuteron structure functions at low x and
large momentum transfer considerably differs from the behavior of the nucleon
structure functions at such conditions. We also argue that for heavier nuclei
the effect of the final state interaction is important even in the Bjorken
limit.
