Three schemes of neutrino mixings (oscillations) together with their mixing
matrices (analogous to Kabibbo-Kobayashi-Maskawa matrices) are considered. In
these schemes neutrino transitions are virtual if neutrino masses are
different. Two of them belong to the so called mass mixing schemes (mixing
parameters are expressed by elements of mass matrices) and the third scheme
belongs to the charge mixing scheme (mixing parameters are expressed through
charges). In the first scheme system of 6 equations for determination of the
all elements of the mass matrix (neutrino masses and transition widths) by
using experimental data are obtained. In the second and third ones the neutrino
mixing angles are equal or close to maximal angles (π/4). It is obvious
that the experiment must give an answer to the following question: Which of
these schemes is realized indeed?Comment: LATEX, 13 pages, no figures and table