  Taking into account mixings among neutrino states, the end of the energy
spectrum of the electron in the tritium beta decay is investigated. It is shown
that for real energy resolutions of a spectrometer, $ \Delta E > 0.08$ eV, the
effective electron neutrino mass should [not] be taken in the form
$m_\beta^{(1)} = \sqrt{\sum|U_{ei}|^2 m_i^2} [m_\beta^{(2)} = \sum|U_{ei}|^2
m_i$.
