We suggest that a previously conjectured relation between Structure Functions
(SF) for nuclei and nucleons also links distribution functions (df) for partons
in a nucleus and in nucleons. The above suggestion ensures in principle
identical results for SF F2A​, whether computed with hadronic or partonic
degrees of freedom. In practice there are differences, due to different F2n​
input. We show that the thus defined nuclear parton distribution functions
(pdf) respect standard sumrules. In addition we numerically compare some
moments of nuclear SF, and find agreement between results, using hadronic and
partonic descriptions. We present computations of EMC ratios for both, and
compare those with hadronic predictions and data. In spite of substantial
differences in the participating SF, the two representations produce
approximately the same EMC ratios. The apparent correlation between the above
deviations is ascribed to a sumrule for F2A​. We conclude with a discussion
of alternative approaches to nuclear pdf.Comment: 14 pages, 4 figure