  A major experimental program is presently underway worldwide to determine the
fundamental non-perturbative functions, the Sivers, Boer-Mulders and
transversity distributions, which are vital for an understanding of the
internal structure of the nucleon. However, at present, many simplifying
assumptions are used in extracting these functions from the data. We
demonstrate that if the binning of the data in Q^2 is small enough so that
Q^2-evolution can be neglected inside a bin, then one can obtain stringent
tests of these assumptions. Failure to satisfy these tests implies that the
presently extracted non-perturbative functions are unreliable.
  To this end we consider the measurement of the Sivers, Boer-Mulders and
transversity difference asymmetries for hadrons with opposite charges in SIDIS
reactions with unpolarized and transversely polarized deuteron and proton
targets: l+N\to l'+h+X, h=\pi^\pm ,K^\pm ,h^\pm. Utilizing only charge and
isospin invariance, and applying the above mentioned simplifying assumptions we
obtain several testable relations amongst the measured asymmetries. If these
tests are satisfied then the measured asymmetries determine two different
combinations of the valence-quark transverse momentum dependent distributions,
which can be determined separately without any contributions from the strange
and other sea-quarks.
