Is the observability of sterile neutrino masses consistent with   $\nu-$oscillations?
  It is shown that a 1980 proposal to search for heavy sterile neutrinos by observing the energy of the associated lepton in weak decays rests on an questionable assumption, and that the possibility of such a detection might be inconsistent with the observability of neutrino oscillations. 
R. Ehrlich
hep-ph