  The azimuthal cos{\phi} and cos2{\phi} modulations of the distribution of
hadrons produced in unpolarized semi-inclusive deep-inelastic scattering of
electrons and positrons off hydrogen and deuterium targets have been measured
in the HERMES experiment. For the first time these modulations were determined
in a four-dimensional kinematic space for positively and negatively charged
pions and kaons separately, as well as for unidentified hadrons. These
azimuthal dependences are sensitive to the transverse motion and polarization
of the quarks within the nucleon via, e.g., the Cahn, Boer-Mulders and Collins
effects.
