  In the framework of schemes with mixing of four massive neutrinos, which can
accommodate the atmospheric, solar and LSND ranges of Delta m^2, we show that,
in the whole region of Delta m^2_{LSND} allowed by LSND, the Super-Kamiokande
up-down asymmetry excludes all mass spectra with a group of three close
neutrino masses separated from the fourth mass by the LSND gap of order 1 eV.
Only two schemes with mass spectra in which two pairs of close masses are
separated by the LSND gap can describe the Super-Kamiokande up-down asymmetry
and all other existing neutrino oscillation data.
