On leading charmed meson production in $\pi$-nucleon interactions
  It is shown that the D--meson, whose light quark is the initial-pion valence quark and whose charmed quark is produced in annihilation of valence quarks and has got a large enough momentum, is really a leading meson in reactions like $\pi^- p -> DX$. If such annihilation of valence quarks from initial hadrons is impossible there must be no distinct leading effect. 
V.A. Bednyakov