Atmospheric neutrino challenges
  We briefly review the improvements in the predictions of atmospheric neutrino fluxes since the NOW2000 workshop. In spite of the great progress in calculational technique the predictions are still not exact because of the uncertainties in the two major sets of input - cosmic ray flux and hadronic interactions on light nuclei. 
Todor Stanev (Bartol Research Institute, University of Delaware,   U.S.A)