A general formalism to evaluate time-reversal odd transverse momentum dependent parton distributions (T-odd TMDS) is reviewed and applied to the calculation of the leading-twist quantities, i.e., the Sivers and the Boer-Mulders functions. Two different models of the proton structure, namely a non relativistic constituent quark model and the MIT bag model, have been used. The results obtained in both frameworks fulfill the Burkardt sum rule to a large extent. The calculation of nuclear effects

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... the extraction of neutron single spin asymmetries in semi-inclusive deep inelastic scattering off transversely polarized ^3He is also illustrated. It is found that the nuclear effects described by an Impulse Approximation approach are under theoretical control.