I have read statements which basically suggest that nuetrino oscillation prohibits any strict statement of conservation of lepton number. Is this true or is it possible that nuetrinos produced along with electrons, muons and taus become entangled so that lepton number is still strictly conserved. Also, what do theorist say about this. I am under the impression that we have models of nuetrino oscillation. Do they predict strict conservation of lepton number? Can they even address this question?