A major experimental program is presently underway worldwide to determine the fundamental
nonperturbative 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 Q2 is
small enough so that Q2 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 nonperturbative 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 þ N → l
0 þ h þ X, h ¼ π, K, h. 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.