Relating the proton, neutron and deuteron structure functions in the covariant Bethe-Salpeter formalism

The neutron structure function F2n(x) is evaluated within the kinematic range 10**(-3)<x<1 from the deuteron and proton data by employing relativistic theoretical description of F2D(x) and several assumptions on the hihg-x asymptotics of F2n(x)/F2p(x). It is shown that new measurements of F2D(x) in the range 0.6<x<0.8 would substantially improve understanding of the relation between d and u valence quarks in the limit x -> 1.