spectrum, as well as on the values of the two Majorana CP-violating phases, $\alpha_{21}$ and $\alpha_{31}$ (see eq. (\[effmass2\])), present in the lepton mixing matrix.

The possibility of detecting of CP-violation due to the Majorana CP-violating phases $\alpha_{21}$ and $\alpha_{31}$ if is found to be nonzero in the -decay experiments of the next generation, depends crucially on the precision with which $m_1$ (or $\Sigma$), , $\theta_{\odot}$, , $\sin^2\theta$ and will be measured. It depends also crucially, as we shall see, on the values of $m_1$ or $\Sigma$, of $\theta_{\odot}$ and of $\!\!$. Actually, the accuracy of measurement of in the next generation of - decay experiments, given their sensitivity limits of $\sim (1.5 - 5.0)\times 10^{-2}~{\rm eV}$, depends on the value of $\!\!$. If only an upper limit on $m_1$ will be obtained, the possibility we are discussing will depend on how stringent this upper limit is. In what regards the dependence of on the type of the neutrino mass spectrum (normal versus inverted hierarchy), if the latter will not be determined in neutrino oscillation experiments (see, e.g., [@SPMPiai01; @AMMS00]), the measurement of ${\mbox{$\left|  < \! m  \! > \right| \ $}}\!\! \neq 0$ itself in the next generation of 