  If the present or upcoming searches for neutrinoless double beta decay give a
positive result, the Majorana nature of massive neutrinos will be established.
  From the determination of the value of the effective Majorana mass parameter
|<m>|, it would be possible to obtain information on the type of neutrino mass
spectrum. Assuming 3-neutrino mixing and massive Majorana neutrinos, we discuss
the information a measurement of, or an upper bound on, |<m>| can provide on
the value of the lightest neutrino mass m1. With additional data on the
neutrino masses obtained in tritium beta decay experiments, it might be
possible to establish whether the CP-symmetry is violated in the lepton sector.
This would require very high precision measurements. If CP-invariance holds,
the allowed patterns of the relative CP-parities of the massive Majorana
neutrinos would be determined.
